diff --git a/src/core/builtin_helpers.py b/src/core/builtin_helpers.py
index fa2fe8c..7539ce2 100644
--- a/src/core/builtin_helpers.py
+++ b/src/core/builtin_helpers.py
@@ -226,28 +226,28 @@ def only_parsers_results(context, return_values):
         parents=return_values)
 
 
-def parse_unrecognized(context, tokens, parsers):
+def parse_unrecognized(context, source, parsers):
     """
-    Try to recognize concepts or code from tokens using the given parsers
+    Try to recognize concepts or code from source using the given parsers
     :param context:
-    :param tokens:
+    :param source:
     :param parsers:
     :return:
     """
     steps = [BuiltinConcepts.BEFORE_PARSING, BuiltinConcepts.PARSING, BuiltinConcepts.AFTER_PARSING]
     sheerka = context.sheerka
 
-    with context.push(desc=f"Parsing unrecognized '{tokens}'") as sub_context:
+    with context.push(desc=f"Parsing unrecognized '{source}'") as sub_context:
         # disable all parsers but the following ones
         sub_context.add_preprocess(BaseParser.PREFIX + "*", enabled=False)
         for parser in parsers:
             sub_context.add_preprocess(BaseParser.PREFIX + parser, enabled=True)
 
-        sub_context.add_inputs(source=tokens)
+        sub_context.add_inputs(source=source)
         to_parse = sheerka.ret(
             context.who,
             True,
-            sheerka.new(BuiltinConcepts.USER_INPUT, body=tokens))
+            sheerka.new(BuiltinConcepts.USER_INPUT, body=source))
         res = sheerka.execute(sub_context, to_parse, steps)
         sub_context.add_values(return_values=res)
 
diff --git a/src/core/sheerka/services/SheerkaExecute.py b/src/core/sheerka/services/SheerkaExecute.py
index f04eb71..c6e0659 100644
--- a/src/core/sheerka/services/SheerkaExecute.py
+++ b/src/core/sheerka/services/SheerkaExecute.py
@@ -1,23 +1,178 @@
 import core.utils
+from cache.Cache import Cache
 from core.builtin_concepts import BuiltinConcepts, ReturnValueConcept
 from core.sheerka.services.sheerka_service import BaseService
+from core.tokenizer import Tokenizer, TokenKind, Keywords, Token
 
 NO_MATCH = "** No Match **"
 
 
+class ParserInput:
+    """
+    Helper class that tokenizes the input once for all
+    """
+
+    def __init__(self, text, tokens=None, start=None, end=None, yield_oef=True):
+        self.text = text
+        self.tokens = tokens or None
+        self.length = len(tokens) if tokens else None
+        self.yield_oef = yield_oef
+
+        self.start = start or 0
+        self.end = end + 1 if end else None
+        self.sub_text = None
+        self.sub_tokens = None
+
+        self.pos = None
+        self.token = None
+
+        self.from_tokens = tokens is not None
+
+    def __repr__(self):
+        from_tokens = "from_tokens" if self.from_tokens else ""
+        return f"ParserInput({from_tokens}'{self.text}')"
+
+    def reset(self, yield_oef=True):
+        if self.tokens is None:
+            self.tokens = list(Tokenizer(self.text))
+            self.length = len(self.tokens)
+
+        if self.end is None:
+            self.end = self.length
+
+        self.yield_oef = yield_oef
+        self.pos = self.start - 1
+        self.token = None
+        return self
+
+    def as_text(self, custom_switcher=None, tracker=None):
+        if custom_switcher is None:
+            if self.sub_text:
+                return self.sub_text
+            if self.start == 0 and self.end == self.length:
+                self.sub_text = self.text
+                return self.sub_text
+            self.sub_text = self.get_text_from_tokens(self.tokens[self.start:self.end])
+            return self.sub_text
+        else:
+            return self.get_text_from_tokens(self.as_tokens(), custom_switcher, tracker)
+
+    def as_tokens(self):
+        if self.sub_tokens:
+            return self.sub_tokens
+        if self.start == 0 and self.end == self.length:
+            self.sub_tokens = self.tokens
+            return self.sub_tokens
+        self.sub_tokens = self.tokens[self.start:self.end]
+        return self.sub_tokens
+
+    def next_token(self, skip_whitespace=True):
+        self.pos += 1
+
+        if self.pos >= self.end:
+            if self.yield_oef:
+                self.token = Token(TokenKind.EOF, "", -1, -1, -1)
+            return False
+
+        self.token = self.tokens[self.pos]
+
+        if self.token.type == TokenKind.EOF and not self.yield_oef:
+            return False
+
+        if skip_whitespace:
+            while self.token.type in (TokenKind.WHITESPACE, TokenKind.NEWLINE):
+                self.pos += 1
+                if self.pos == self.end:
+                    return False
+                self.token = self.tokens[self.pos]
+
+        return self.pos < self.end
+
+    def is_empty(self):
+        if self.text.strip() == "":
+            return True
+
+        if self.end == self.start:
+            return True
+
+        if self.end and self.end == self.start + 1 and self.tokens[self.start].type == TokenKind.WHITESPACE:
+            return True
+        return False
+
+    @staticmethod
+    def get_text_from_tokens(tokens, custom_switcher=None, tracker=None):
+        """
+        Create the source code, from the list of token
+        :param tokens: list of tokens
+        :param custom_switcher: to override the behaviour (the return value) of some token
+        :param tracker: keep track of the original token value when custom switched
+        :return:
+        """
+        if tokens is None:
+            return ""
+        res = ""
+
+        if not hasattr(tokens, "__iter__"):
+            tokens = [tokens]
+
+        switcher = {
+            TokenKind.KEYWORD: lambda t: Keywords(t.value).value,
+            TokenKind.CONCEPT: lambda t: core.utils.str_concept(t.value),
+        }
+
+        if custom_switcher:
+            switcher.update(custom_switcher)
+
+        for token in tokens:
+            value = switcher.get(token.type, lambda t: t.value)(token)
+            res += value
+            if tracker is not None and token.type in custom_switcher:
+                tracker[value] = token.value
+        return res
+
+
 class SheerkaExecute(BaseService):
     """
     Manage the execution of a process flow
     """
 
     NAME = "Execute"
+    PARSERS_INPUTS_ENTRY = "ParserInput"  # entry for admin or internal variables
 
     def __init__(self, sheerka):
         super().__init__(sheerka)
-        
+        self.pi_cache = None
+
     def initialize(self):
         self.sheerka.bind_service_method(self.execute)
 
+        self.pi_cache = Cache(default=lambda key: ParserInput(key), max_size=20)
+        self.sheerka.cache_manager.register_cache(self.PARSERS_INPUTS_ENTRY, self.pi_cache, False)
+
+    def get_parser_input(self, text, tokens=None):
+        """
+        Returns new or existing parser input
+        :param text:
+        :param tokens:
+        :param length:
+        :return:
+        """
+
+        if isinstance(text, ParserInput):
+            return text
+
+        if tokens is None or self.pi_cache.has(text):
+            pi = self.pi_cache.get(text)
+            if pi is None:  # when CacheManager.cache_only is True
+                pi = ParserInput(text)
+                self.pi_cache.put(text, pi)
+            return pi
+
+        key = text or ParserInput.get_text_from_tokens(tokens)
+        pi = ParserInput(key, tokens)
+        self.pi_cache.put(key, pi)
+        return pi
+
     def call_parsers(self, context, return_values):
 
         # return_values must be a list
@@ -56,7 +211,7 @@ class SheerkaExecute(BaseService):
 
                 for return_value in inputs_for_this_group:
 
-                    to_parse = return_value.body.body \
+                    to_parse = self.get_parser_input(return_value.body.body) \
                         if self.sheerka.isinstance(return_value.body, BuiltinConcepts.USER_INPUT) \
                         else return_value.body
 
diff --git a/src/core/tokenizer.py b/src/core/tokenizer.py
index 6d4be35..67af9e6 100644
--- a/src/core/tokenizer.py
+++ b/src/core/tokenizer.py
@@ -104,6 +104,9 @@ class Token:
         else:
             return str(self.value)
 
+    def clone(self):
+        return Token(self.type, self.value, self.index, self.line, self.column)
+
 
 @dataclass()
 class LexerError(Exception):
diff --git a/src/evaluators/AddConceptInSetEvaluator.py b/src/evaluators/AddConceptInSetEvaluator.py
index 0e182dd..85a368e 100644
--- a/src/evaluators/AddConceptInSetEvaluator.py
+++ b/src/evaluators/AddConceptInSetEvaluator.py
@@ -1,5 +1,6 @@
 import core.builtin_helpers
 from core.builtin_concepts import ParserResultConcept, BuiltinConcepts
+from core.sheerka.services.SheerkaExecute import SheerkaExecute
 from evaluators.BaseEvaluator import OneReturnValueEvaluator
 from parsers.DefaultParser import IsaConceptNode
 
@@ -28,10 +29,11 @@ class AddConceptInSetEvaluator(OneReturnValueEvaluator):
     def eval(self, context, return_value):
 
         def _resolve(name_node):
+            parser_input = context.sheerka.services[SheerkaExecute.NAME].get_parser_input(None, name_node.tokens)
             ret_val = sheerka.ret(
                 self.name,
                 True,
-                sheerka.new(BuiltinConcepts.USER_INPUT, body=name_node.tokens, user_name="N/A"))
+                sheerka.new(BuiltinConcepts.USER_INPUT, body=parser_input, user_name="N/A"))
 
             with context.push(desc=f"Recognizing '{name_node}'") as sub_context:
                 r = sheerka.execute(sub_context, ret_val, ALL_STEPS)
diff --git a/src/evaluators/LexerNodeEvaluator.py b/src/evaluators/LexerNodeEvaluator.py
index 4ccb348..593d810 100644
--- a/src/evaluators/LexerNodeEvaluator.py
+++ b/src/evaluators/LexerNodeEvaluator.py
@@ -7,7 +7,7 @@ from parsers.PythonParser import LexerNodeParserHelperForPython, PythonNode
 
 class LexerNodeEvaluator(OneReturnValueEvaluator):
     """
-    After a BNF is recognized, generates the concept or the list concepts
+    Evaluate a list of LexerNode (ConceptNode | SourceCodeNode | UnrecognizedTokenNode...)
     """
 
     NAME = "LexerNode"
diff --git a/src/parsers/AtomNodeParser.py b/src/parsers/AtomNodeParser.py
index 465054e..a2f73ac 100644
--- a/src/parsers/AtomNodeParser.py
+++ b/src/parsers/AtomNodeParser.py
@@ -3,6 +3,7 @@ from dataclasses import dataclass
 from core import builtin_helpers
 from core.builtin_concepts import BuiltinConcepts
 from core.concept import DEFINITION_TYPE_BNF, Concept
+from core.sheerka.services.SheerkaExecute import ParserInput
 from core.tokenizer import Tokenizer
 from core.utils import strip_tokens
 from parsers.BaseNodeParser import BaseNodeParser, ConceptNode, UnrecognizedTokensNode, SourceCodeNode
@@ -250,26 +251,27 @@ class AtomNodeParser(BaseNodeParser):
 
         concept_parser_helpers = [AtomConceptParserHelper(self.context)]
 
-        while self.next_token(False):
+        while self.parser_input.next_token(False):
             for concept_parser in concept_parser_helpers:
                 concept_parser.reset()
 
-            token = self.token
+            token = self.parser_input.token
+            pos = self.parser_input.pos
 
             try:
                 for concept_parser in concept_parser_helpers:
-                    if concept_parser.eat_token(self.token, self.pos):
+                    if concept_parser.eat_token(token, pos):
                         concept_parser.lock()
 
                 concepts = self.get_concepts(token, self._is_eligible, custom=_get_concepts_by_name)
                 if not concepts:
                     for concept_parser in concept_parser_helpers:
-                        concept_parser.eat_unrecognized(token, self.pos)
+                        concept_parser.eat_unrecognized(token, pos)
                     continue
 
                 if len(concepts) == 1:
                     for concept_parser in concept_parser_helpers:
-                        concept_parser.eat_concept(concepts[0], self.pos)
+                        concept_parser.eat_concept(concepts[0], pos)
                     continue
 
                 # make the cartesian product
@@ -284,7 +286,7 @@ class AtomNodeParser(BaseNodeParser):
                     for concept in concepts:
                         clone = concept_parser.clone()
                         temp_res.append(clone)
-                        clone.eat_concept(concept, self.pos)
+                        clone.eat_concept(concept, pos)
 
                 concept_parser_helpers = temp_res
             finally:
@@ -298,22 +300,26 @@ class AtomNodeParser(BaseNodeParser):
 
         return concept_parser_helpers
 
-    def get_by_name(self, parser_input):
+    def get_by_name(self):
         """
         Try to recognize the full parser input as a concept name
         :return:
         """
-        source = self.get_input_as_text(parser_input)
+        source = self.parser_input.as_text()
         concepts = self.sheerka.get_by_name(source.strip())
         if not self.sheerka.is_known(concepts):
             return None
 
         concepts = [concepts] if isinstance(concepts, Concept) else concepts
         res = []
-        start, end = self.get_tokens_boundaries(self.tokens)
+        start, end = self.get_tokens_boundaries(self.parser_input.as_tokens())
         for concept in concepts:
             parser_helper = AtomConceptParserHelper(None)
-            parser_helper.sequence.append(ConceptNode(concept, start, end, strip_tokens(self.tokens, True), source))
+            parser_helper.sequence.append(ConceptNode(
+                concept,
+                start,
+                end,
+                strip_tokens(self.parser_input.as_tokens(), True), source))
             res.append(parser_helper)
 
         return res
@@ -331,7 +337,7 @@ class AtomNodeParser(BaseNodeParser):
                 if isinstance(node, ConceptNode):
                     if len(node.concept.metadata.variables) > 0:
                         node.concept.metadata.is_evaluated = True  # Do not try to evaluate those concepts
-                node.tokens = self.tokens[node.start:node.end + 1]
+                node.tokens = self.parser_input.tokens[node.start:node.end + 1]
                 node.fix_source()
 
             if parser_helper in valid_parser_helpers:
@@ -341,8 +347,8 @@ class AtomNodeParser(BaseNodeParser):
 
         return valid_parser_helpers
 
-    def parse(self, context, parser_input):
-        if parser_input == "":
+    def parse(self, context, parser_input: ParserInput):
+        if parser_input.is_empty():
             return context.sheerka.ret(
                 self.name,
                 False,
@@ -356,7 +362,7 @@ class AtomNodeParser(BaseNodeParser):
                 context.sheerka.new(BuiltinConcepts.ERROR, body=self.error_sink))
 
         sequences = self.get_concepts_sequences()
-        if by_name := self.get_by_name(parser_input):
+        if by_name := self.get_by_name():
             sequences.extend(by_name)
 
         parser_helpers = self.get_valid(sequences)
@@ -386,4 +392,4 @@ class AtomNodeParser(BaseNodeParser):
             return self.sheerka.ret(
                 self.name,
                 False,
-                context.sheerka.new(BuiltinConcepts.NOT_FOR_ME, body=parser_input))
+                context.sheerka.new(BuiltinConcepts.NOT_FOR_ME, body=parser_input.as_text()))
diff --git a/src/parsers/BaseNodeParser.py b/src/parsers/BaseNodeParser.py
index 2b62af3..3ee27f8 100644
--- a/src/parsers/BaseNodeParser.py
+++ b/src/parsers/BaseNodeParser.py
@@ -5,7 +5,7 @@ from enum import Enum
 import core.utils
 from core.builtin_concepts import BuiltinConcepts
 from core.concept import VARIABLE_PREFIX, Concept, DEFINITION_TYPE_BNF, ConceptParts
-from core.sheerka.ExecutionContext import ExecutionContext
+from core.sheerka.services.SheerkaExecute import ParserInput
 from core.tokenizer import TokenKind, LexerError, Token, Keywords
 from parsers.BaseParser import Node, BaseParser, ErrorNode
 
@@ -86,7 +86,6 @@ class UnrecognizedTokensNode(LexerNode):
             else:
                 self.end -= 1
 
-
     def has_open_paren(self):
         return self.parenthesis_count > 0
 
@@ -598,13 +597,13 @@ class BaseNodeParser(BaseParser):
         else:
             self.concepts_by_first_keyword = None
 
-        self.token = None
-        self.pos = -1
-        self.tokens = None
-
-        self.context: ExecutionContext = None
-        self.text = None
-        self.sheerka = None
+        # self.token = None
+        # self.pos = -1
+        # self.tokens = None
+        #
+        # self.context: ExecutionContext = None
+        # self.text = None
+        # self.sheerka = None
 
     def init_from_concepts(self, context, concepts, **kwargs):
         """
@@ -617,43 +616,48 @@ class BaseNodeParser(BaseParser):
         concepts_by_first_keyword = self.get_concepts_by_first_keyword(context, concepts).body
         self.concepts_by_first_keyword = self.resolve_concepts_by_first_keyword(context, concepts_by_first_keyword).body
 
-    def reset_parser(self, context, text):
+    def reset_parser(self, context, parser_input: ParserInput):
         self.context = context
         self.sheerka = context.sheerka
-        self.text = text
-
+        self.parser_input = parser_input
         try:
-            self.tokens = list(self.get_input_as_tokens(text))
+            self.parser_input.reset(False)
         except LexerError as e:
             self.add_error(self.sheerka.new(BuiltinConcepts.ERROR, body=e), False)
             return False
-
-        self.token = None
-        self.pos = -1
         return True
+        # self.text = text
+        #
+        # try:
+        #     self.tokens = list(self.get_input_as_tokens(text))
+        #
+        #
+        # self.token = None
+        # self.pos = -1
+        # return True
 
-    def add_error(self, error, next_token=True):
-        self.error_sink.append(error)
-        if next_token:
-            self.next_token()
-        return error
+    # def add_error(self, error, next_token=True):
+    #     self.error_sink.append(error)
+    #     if next_token:
+    #         self.parser_input.next_token()
+    #     return error
 
-    def get_token(self) -> Token:
-        return self.token
-
-    def next_token(self, skip_whitespace=True):
-        if self.token and self.token.type == TokenKind.EOF:
-            return False
-
-        self.pos += 1
-        self.token = self.tokens[self.pos]
-
-        if skip_whitespace:
-            while self.token.type == TokenKind.WHITESPACE or self.token.type == TokenKind.NEWLINE:
-                self.pos += 1
-                self.token = self.tokens[self.pos]
-
-        return self.token.type != TokenKind.EOF
+    # def get_token(self) -> Token:
+    #     return self.token
+    #
+    # def next_token(self, skip_whitespace=True):
+    #     if self.token and self.token.type == TokenKind.EOF:
+    #         return False
+    #
+    #     self.pos += 1
+    #     self.token = self.tokens[self.pos]
+    #
+    #     if skip_whitespace:
+    #         while self.token.type == TokenKind.WHITESPACE or self.token.type == TokenKind.NEWLINE:
+    #             self.pos += 1
+    #             self.token = self.tokens[self.pos]
+    #
+    #     return self.token.type != TokenKind.EOF
 
     def get_concepts(self, token, to_keep, custom=None, to_map=None, strip_quotes=False):
         """
diff --git a/src/parsers/BaseParser.py b/src/parsers/BaseParser.py
index ad58427..dcf32c5 100644
--- a/src/parsers/BaseParser.py
+++ b/src/parsers/BaseParser.py
@@ -9,6 +9,25 @@ from core.sheerka_logger import get_logger
 from core.tokenizer import TokenKind, Keywords, Token, Tokenizer
 
 
+# # keep a cache for the parser input
+# pi_cache = Cache(default=lambda key: ParserInput(key), max_size=20)
+#
+#
+# def get_parser_input(text, tokens=None, length=None):
+#     """
+#     Returns new or existing parser input
+#     :param text:
+#     :param tokens:
+#     :param length:
+#     :return:
+#     """
+#     if tokens is None or pi_cache.has(text):
+#         return pi_cache.get(text)
+#     pi = ParserInput(text, tokens, length)
+#     pi_cache.put(text, pi)
+#     return pi
+
+
 @dataclass()
 class Node:
     pass
@@ -84,6 +103,9 @@ class BaseParser:
         self.enabled = enabled
 
         self.error_sink = []
+        self.context: ExecutionContext = None
+        self.sheerka = None
+        self.parser_input: ParserInput = None
 
     def __eq__(self, other):
         if not isinstance(other, self.__class__):
@@ -99,6 +121,12 @@ class BaseParser:
     def parse(self, context, parser_input):
         pass
 
+    def add_error(self, error, next_token=True):
+        self.error_sink.append(error)
+        if next_token:
+            self.parser_input.next_token()
+        return error
+
     @property
     def has_error(self):
         return len(self.error_sink) > 0
diff --git a/src/parsers/BnfNodeParser.py b/src/parsers/BnfNodeParser.py
index dd2d24d..dd44cf7 100644
--- a/src/parsers/BnfNodeParser.py
+++ b/src/parsers/BnfNodeParser.py
@@ -14,6 +14,7 @@ from cache.Cache import Cache
 from core import builtin_helpers
 from core.builtin_concepts import BuiltinConcepts
 from core.concept import Concept, DEFINITION_TYPE_BNF, DoNotResolve, ConceptParts
+from core.sheerka.services.SheerkaExecute import ParserInput
 from core.tokenizer import Tokenizer, Token, TokenKind
 from parsers.BaseNodeParser import BaseNodeParser, LexerNode, UnrecognizedTokensNode, ConceptNode, GrammarErrorNode
 from parsers.BaseParser import ErrorNode
@@ -149,7 +150,7 @@ class ConceptExpression(ParsingExpression):
         return NonTerminalNode(self,
                                node.start,
                                node.end,
-                               parser_helper.parser.tokens[node.start: node.end + 1],
+                               parser_helper.parser.parser_input.tokens[node.start: node.end + 1],
                                [node])
 
 
@@ -184,7 +185,11 @@ class Sequence(ParsingExpression):
                     children.append(node)
                     end_pos = node.end
 
-        return NonTerminalNode(self, init_pos, end_pos, parser_helper.parser.tokens[init_pos: end_pos + 1], children)
+        return NonTerminalNode(self,
+                               init_pos,
+                               end_pos,
+                               parser_helper.parser.parser_input.tokens[init_pos: end_pos + 1],
+                               children)
 
     def __repr__(self):
         to_str = ", ".join(repr(n) for n in self.elements)
@@ -206,7 +211,7 @@ class OrderedChoice(ParsingExpression):
                 return NonTerminalNode(self,
                                        init_pos,
                                        node.end,
-                                       parser_helper.parser.tokens[init_pos: node.end + 1],
+                                       parser_helper.parser.parser_input.tokens[init_pos: node.end + 1],
                                        [node])
 
             parser_helper.seek(init_pos)  # backtrack
@@ -237,7 +242,7 @@ class Optional(ParsingExpression):
                         self,
                         node.start,
                         node.end,
-                        parser_helper.parser.tokens[node.start: node.end + 1],
+                        parser_helper.parser.parser_input.tokens[node.start: node.end + 1],
                         [node])
 
             parser_helper.seek(init_pos)  # backtrack
@@ -303,7 +308,8 @@ class ZeroOrMore(Repetition):
         if len(children) == 0:
             return NonTerminalNode(self, init_pos, -1, [], [])
 
-        return NonTerminalNode(self, init_pos, end_pos, parser_helper.parser.tokens[init_pos: end_pos + 1], children)
+        return NonTerminalNode(self, init_pos, end_pos, parser_helper.parser.parser_input.tokens[init_pos: end_pos + 1],
+                               children)
 
     def __repr__(self):
         to_str = ", ".join(repr(n) for n in self.elements)
@@ -343,7 +349,11 @@ class OneOrMore(Repetition):
         if len(children) == 0:  # if nothing is found, it's an error
             return None
 
-        return NonTerminalNode(self, init_pos, end_pos, parser_helper.parser.tokens[init_pos: end_pos + 1], children)
+        return NonTerminalNode(self,
+                               init_pos,
+                               end_pos,
+                               parser_helper.parser.parser_input.tokens[init_pos: end_pos + 1],
+                               children)
 
     def __repr__(self):
         to_str = ", ".join(repr(n) for n in self.elements)
@@ -507,24 +517,24 @@ class BnfConceptParserHelper:
             return False
 
         self.pos += 1
-        self.token = self.parser.tokens[self.pos]
+        self.token = self.parser.parser_input.tokens[self.pos]
 
         if skip_whitespace:
             while self.token.type == TokenKind.WHITESPACE or self.token.type == TokenKind.NEWLINE:
                 self.pos += 1
-                self.token = self.parser.tokens[self.pos]
+                self.token = self.parser.parser_input.tokens[self.pos]
 
         return self.token.type != TokenKind.EOF
 
     def seek(self, pos):
         self.pos = pos
-        self.token = self.parser.tokens[self.pos]
+        self.token = self.parser.parser_input.tokens[self.pos]
 
     def has_error(self):
         return len(self.errors) > 0
 
     def is_locked(self):
-        return self.parser.pos <= self.pos or self.has_error()
+        return self.parser.parser_input.pos <= self.pos or self.has_error()
 
     def eat_concept(self, concept, token):
         if self.is_locked():
@@ -546,8 +556,8 @@ class BnfConceptParserHelper:
             self.errors.append(GrammarErrorNode(error_msg))
             return
 
-        self.pos = self.parser.pos
-        self.token = self.parser.tokens[self.pos]
+        self.pos = self.parser.parser_input.pos
+        self.token = self.parser.parser_input.tokens[self.pos]
 
         # parse
         node = parsing_expression.parse(self)
@@ -557,15 +567,15 @@ class BnfConceptParserHelper:
             self.bnf_parsed = True
         else:
             self.debug.append(("Rewind", token))
-            self.unrecognized_tokens.add_token(token, self.parser.pos)
-            self.pos = self.parser.pos  # reset position
+            self.unrecognized_tokens.add_token(token, self.parser.parser_input.pos)
+            self.pos = self.parser.parser_input.pos  # reset position
 
     def eat_unrecognized(self, token):
         if self.is_locked():
             return
 
         self.debug.append(token)
-        self.unrecognized_tokens.add_token(token, self.parser.pos)
+        self.unrecognized_tokens.add_token(token, self.parser.parser_input.pos)
 
     def manage_unrecognized(self):
         if self.unrecognized_tokens.is_empty():
@@ -631,7 +641,7 @@ class BnfConceptParserHelper:
             concept,
             underlying.start,
             underlying.end,
-            self.parser.tokens[underlying.start: underlying.end + 1],
+            self.parser.parser_input.tokens[underlying.start: underlying.end + 1],
             None,
             underlying)
         return concept_node
@@ -779,9 +789,9 @@ class BnfNodeParser(BaseNodeParser):
 
         concept_parser_helpers = [BnfConceptParserHelper(self)]
 
-        while self.next_token(False):
+        while self.parser_input.next_token(False):
 
-            token = self.get_token()
+            token = self.parser_input.token
 
             try:
                 concepts = self.get_concepts(token, self._is_eligible, strip_quotes=False)
@@ -837,7 +847,7 @@ class BnfNodeParser(BaseNodeParser):
             resolved = self.resolve_parsing_expression(expression, already_seen or set())
             sub_context.add_values(return_values=resolved)
 
-            self.concepts_grammars.put(concept.id,  resolved)
+            self.concepts_grammars.put(concept.id, resolved)
 
             if self.has_error:
                 return None
@@ -929,7 +939,7 @@ class BnfNodeParser(BaseNodeParser):
             return self.context.concepts[concept]
         return self.sheerka.get_by_key(concept)
 
-    def parse(self, context, parser_input):
+    def parse(self, context, parser_input: ParserInput):
         """
         parser_input can be string, but text can also be an list of tokens
         :param context:
@@ -940,11 +950,11 @@ class BnfNodeParser(BaseNodeParser):
         context.log(f"Parsing '{parser_input}' with BnfNode", self.name)
         sheerka = context.sheerka
 
-        if parser_input == "" or isinstance(parser_input, list) and len(parser_input) == 0:
+        if parser_input.is_empty():
             return sheerka.ret(self.name,
                                False,
                                sheerka.new(BuiltinConcepts.NOT_FOR_ME,
-                                           body=parser_input,
+                                           body=parser_input.as_text(),
                                            reason=BuiltinConcepts.IS_EMPTY))
 
         if not self.reset_parser(context, parser_input):
@@ -966,7 +976,7 @@ class BnfNodeParser(BaseNodeParser):
             return self.sheerka.ret(
                 self.name,
                 False,
-                context.sheerka.new(BuiltinConcepts.NOT_FOR_ME, body=parser_input))
+                context.sheerka.new(BuiltinConcepts.NOT_FOR_ME, body=parser_input.as_text()))
 
         ret = []
         for parser_helper in valid_parser_helpers:
@@ -977,13 +987,13 @@ class BnfNodeParser(BaseNodeParser):
                     self.sheerka.new(
                         BuiltinConcepts.PARSER_RESULT,
                         parser=self,
-                        source=parser_input,
+                        source=parser_input.as_text(),
                         body=parser_helper.sequence,
                         try_parsed=parser_helper.sequence)))
 
         if len(ret) == 1:
-            self.log_result(context, parser_input, ret[0])
+            self.log_result(context, parser_input.as_text(), ret[0])
             return ret[0]
         else:
-            self.log_multiple_results(context, parser_input, ret)
+            self.log_multiple_results(context, parser_input.as_text(), ret)
             return ret
diff --git a/src/parsers/BnfParser.py b/src/parsers/BnfParser.py
index 8382b35..79dd750 100644
--- a/src/parsers/BnfParser.py
+++ b/src/parsers/BnfParser.py
@@ -115,7 +115,6 @@ class BnfParser(BaseParser):
 
     def parse(self, context: ExecutionContext, parser_input):
 
-        tree = None
         try:
             self.reset_parser(context, parser_input)
             tree = self.parse_choice()
@@ -124,7 +123,10 @@ class BnfParser(BaseParser):
             if token and token.type != TokenKind.EOF:
                 self.add_error(UnexpectedTokenErrorNode(f"Unexpected token '{token}'", token, []))
         except LexerError as e:
-            self.add_error(e, False)
+            return self.sheerka.ret(
+                self.name,
+                False,
+                context.sheerka.new(BuiltinConcepts.ERROR, body=[e]))
 
         value = self.get_return_value_body(context.sheerka, self.source, tree, tree)
 
@@ -283,4 +285,3 @@ class BnfParser(BaseParser):
         expression.rule_name = token.value
         self.next_token()
         return expression
-
diff --git a/src/parsers/DefaultParser.py b/src/parsers/DefaultParser.py
index e250d1b..6093c48 100644
--- a/src/parsers/DefaultParser.py
+++ b/src/parsers/DefaultParser.py
@@ -1,12 +1,13 @@
-from core.builtin_concepts import BuiltinConcepts, ReturnValueConcept, ParserResultConcept
-from core.concept import ConceptParts, DEFINITION_TYPE_BNF, DEFINITION_TYPE_DEF
+from dataclasses import dataclass, field
+
 import core.builtin_helpers
 import core.utils
+from core.builtin_concepts import BuiltinConcepts, ReturnValueConcept, ParserResultConcept
+from core.concept import ConceptParts, DEFINITION_TYPE_BNF, DEFINITION_TYPE_DEF
+from core.sheerka.services.SheerkaExecute import ParserInput, SheerkaExecute
+from core.tokenizer import Tokenizer, TokenKind, Keywords
 from parsers.BaseParser import BaseParser, Node, ErrorNode, NotInitializedNode
-from core.tokenizer import Tokenizer, TokenKind, Token, Keywords
-from dataclasses import dataclass, field
 from parsers.BnfParser import BnfParser
-from core.sheerka.Sheerka import ExecutionContext
 
 
 @dataclass()
@@ -90,11 +91,10 @@ class DefConceptNode(DefaultParserNode):
         asts = {}
         for part_key in ConceptParts:
             prop_value = getattr(self, part_key.value)
-            if isinstance(prop_value, ReturnValueConcept) and isinstance(prop_value.body,
-                                                                         ParserResultConcept) and hasattr(
-                prop_value.body.body, "ast_"):
+            if isinstance(prop_value, ReturnValueConcept) and \
+                isinstance(prop_value.body, ParserResultConcept) and \
+                hasattr(prop_value.body.body, "ast_"):
                 asts[part_key] = prop_value
-                # asts[part_key] = prop_value.body.body.ast_
         return asts
 
 
@@ -111,11 +111,6 @@ class DefaultParser(BaseParser):
 
     def __init__(self, **kwargs):
         BaseParser.__init__(self, "Default", 60)
-        self.lexer_iter = None
-        self._current = None
-        self.context: ExecutionContext = None
-        self.text = None
-        self.sheerka = None
 
     @staticmethod
     def fix_indentation(tokens):
@@ -129,6 +124,7 @@ class DefaultParser(BaseParser):
         :param tokens:
         :return:
         """
+        tokens = tokens.copy()  # do not modify ParserInput.tokens
         if tokens[0].type != TokenKind.COLON:
             return tokens
 
@@ -143,6 +139,8 @@ class DefaultParser(BaseParser):
         indent_size = len(tokens[2].value)
 
         # now fix the other indentations
+        # KSI 23/05/2020 Not quite sure this 'fixing' stuff is still relevant,
+        #   as I now have an editor in interactive mode
         i = 3
         while i < len(tokens) - 1:
             if tokens[i].type == TokenKind.NEWLINE:
@@ -152,44 +150,22 @@ class DefaultParser(BaseParser):
                 if len(tokens[i + 1].value) < indent_size:
                     return SyntaxErrorNode([tokens[i + 1]], "Invalid indentation.")
 
+                tokens[i + 1] = tokens[i + 1].clone()
                 tokens[i + 1].value = " " * (len(tokens[i + 1].value) - indent_size)
             i += 1
 
         return tokens[3:]
 
-    def reset_parser(self, context, text):
+    def reset_parser(self, context, parser_input):
         self.context = context
         self.sheerka = context.sheerka
+        self.parser_input = parser_input
+        self.parser_input.reset()
+        self.parser_input.next_token()
 
-        self.text = text
-        self.lexer_iter = iter(Tokenizer(text))
-        self._current = None
-
-        self.next_token()
-
-    def add_error(self, error, next_token=True):
-        self.error_sink.append(error)
-        if next_token:
-            self.next_token()
-        return error
-
-    def get_token(self) -> Token:
-        return self._current
-
-    def next_token(self, skip_whitespace=True):
-        try:
-            self._current = next(self.lexer_iter)
-            if skip_whitespace:
-                while self._current.type == TokenKind.WHITESPACE or self._current.type == TokenKind.NEWLINE:
-                    self._current = next(self.lexer_iter)
-        except StopIteration:
-            self._current = None
-
-        return
-
-    def parse(self, context, parser_input):
+    def parse(self, context, parser_input: ParserInput):
         # default parser can only manage string text
-        if not isinstance(parser_input, str):
+        if parser_input.from_tokens:
             ret = context.sheerka.ret(
                 self.name,
                 False,
@@ -197,12 +173,14 @@ class DefaultParser(BaseParser):
             self.log_result(context, parser_input, ret)
             return ret
 
-        tree = None
         try:
             self.reset_parser(context, parser_input)
             tree = self.parse_statement()
         except core.tokenizer.LexerError as e:
-            self.add_error(e, False)
+            return self.sheerka.ret(
+                self.name,
+                False,
+                context.sheerka.new(BuiltinConcepts.ERROR, body=[e]))
 
         # If a error is found it must be sent to error_sink
         # tree must contain what was recognized
@@ -210,26 +188,20 @@ class DefaultParser(BaseParser):
         if self.has_error and isinstance(self.error_sink[0], CannotHandleErrorNode):
             body = self.sheerka.new(BuiltinConcepts.NOT_FOR_ME, body=self.error_sink)
         else:
-            body = self.get_return_value_body(context.sheerka, parser_input, tree, tree)
-            # body = self.sheerka.new(
-            #     BuiltinConcepts.PARSER_RESULT,
-            #     parser=self,
-            #     source=text,
-            #     body=self.error_sink if self.has_error else tree,
-            #     try_parsed=tree)
+            body = self.get_return_value_body(context.sheerka, parser_input.as_text(), tree, tree)
 
         ret = self.sheerka.ret(
             self.name,
             not self.has_error,
             body)
 
-        self.log_result(context, parser_input, ret)
+        self.log_result(context, parser_input.as_text(), ret)
         return ret
 
     def parse_statement(self):
-        token = self.get_token()
+        token = self.parser_input.token
         if token.value == Keywords.DEF:
-            self.next_token()
+            self.parser_input.next_token()
             self.context.log("Keyword DEF found.", self.name)
             return self.parse_def_concept(token)
         else:
@@ -282,23 +254,23 @@ class DefaultParser(BaseParser):
             return concept_name
 
         keyword = []
-        token = self.get_token()
+        token = self.parser_input.token
         if token.value != Keywords.ISA:
             return self.add_error(CannotHandleErrorNode([token], ""))
         keyword.append(token)
-        self.next_token()
+        self.parser_input.next_token()
 
         set_name = self.parse_concept_name()
         return IsaConceptNode(keyword, concept_name, set_name)
 
     def parse_concept_name(self):
         tokens = []
-        token = self.get_token()
+        token = self.parser_input.token
 
         while not (token.type == TokenKind.EOF or token.type == TokenKind.KEYWORD):
             tokens.append(token)
-            self.next_token()
-            token = self.get_token()
+            self.parser_input.next_token()
+            token = self.parser_input.token
 
         if len(tokens) == 0:
             return self.add_error(UnexpectedTokenErrorNode([token], "Unexpected token", []))
@@ -319,7 +291,7 @@ class DefaultParser(BaseParser):
             Keywords.POST: None,
         }
         current_part = Keywords.CONCEPT
-        token = self.get_token()
+        token = self.parser_input.token
         first_token = token
 
         # loop thru the tokens, and put them in the correct tokens_found_by_parts entry
@@ -334,18 +306,18 @@ class DefaultParser(BaseParser):
                 else:
                     tokens_found_by_parts[keyword] = [token]
                 current_part = keyword
-                self.next_token()
+                self.parser_input.next_token()
             else:
                 tokens_found_by_parts[current_part].append(token)
-                self.next_token(False)
+                self.parser_input.next_token(False)
 
-            token = self.get_token()
+            token = self.parser_input.token
 
         return first_token, tokens_found_by_parts
 
     def get_concept_name(self, first_token, tokens_found_by_parts):
         name_first_token_index = 1
-        token = self.get_token()
+        token = self.parser_input.token
         if first_token.value != Keywords.CONCEPT:
             self.add_error(UnexpectedTokenErrorNode([token], "Syntax error.", [Keywords.CONCEPT]))
             name_first_token_index = 0
@@ -431,10 +403,11 @@ class DefaultParser(BaseParser):
 
             # ask the other parsers if they recognize the tokens
             with self.context.push(self.name, desc=f"Parsing {keyword}") as sub_context:
+                parser_input = self.sheerka.services[SheerkaExecute.NAME].get_parser_input(None, tokens)
                 to_parse = self.sheerka.ret(
                     sub_context.who,
                     True,
-                    self.sheerka.new(BuiltinConcepts.USER_INPUT, body=tokens))
+                    self.sheerka.new(BuiltinConcepts.USER_INPUT, body=parser_input))
                 steps = [BuiltinConcepts.PARSING]
                 parsed = self.sheerka.execute(sub_context, to_parse, steps)
                 parsing_result = core.builtin_helpers.expect_one(sub_context, parsed)
diff --git a/src/parsers/EmptyStringParser.py b/src/parsers/EmptyStringParser.py
index 7663377..46f6a15 100644
--- a/src/parsers/EmptyStringParser.py
+++ b/src/parsers/EmptyStringParser.py
@@ -1,4 +1,5 @@
 from core.builtin_concepts import BuiltinConcepts
+from core.sheerka.services.SheerkaExecute import ParserInput
 from parsers.BaseParser import BaseParser
 
 
@@ -10,12 +11,10 @@ class EmptyStringParser(BaseParser):
     def __init__(self, **kwargs):
         BaseParser.__init__(self, "EmptyString", 90)
 
-    def parse(self, context, parser_input):
+    def parse(self, context, parser_input: ParserInput):
         sheerka = context.sheerka
 
-        if isinstance(parser_input, str) and parser_input.strip() == "" or \
-            isinstance(parser_input, list) and parser_input == [] or \
-            parser_input is None:
+        if parser_input.is_empty():
             ret = sheerka.ret(self.name, True, sheerka.new(
                 BuiltinConcepts.PARSER_RESULT,
                 parser=self,
diff --git a/src/parsers/ExactConceptParser.py b/src/parsers/ExactConceptParser.py
index 35338b8..453bba8 100644
--- a/src/parsers/ExactConceptParser.py
+++ b/src/parsers/ExactConceptParser.py
@@ -1,11 +1,12 @@
 import logging
 
+import core.builtin_helpers
 from core.builtin_concepts import ReturnValueConcept, BuiltinConcepts
 from core.concept import VARIABLE_PREFIX
+from core.sheerka.services.SheerkaExecute import ParserInput
 from core.tokenizer import Keywords, TokenKind, LexerError
 from core.utils import str_concept
 from parsers.BaseParser import BaseParser
-import core.builtin_helpers
 
 
 class ExactConceptParser(BaseParser):
@@ -19,7 +20,7 @@ class ExactConceptParser(BaseParser):
         BaseParser.__init__(self, "ExactConcept", 80)
         self.max_word_size = max_word_size
 
-    def parse(self, context, parser_input):
+    def parse(self, context, parser_input: ParserInput):
         """
         text can be string, but text can also be an list of tokens
         :param context:
@@ -31,6 +32,7 @@ class ExactConceptParser(BaseParser):
         sheerka = context.sheerka
 
         try:
+            parser_input.reset()
             words = self.get_words(parser_input)
         except LexerError as e:
             context.log(f"Error found in tokenizer {e}", self.name)
@@ -38,8 +40,8 @@ class ExactConceptParser(BaseParser):
 
         if len(words) > (self.max_word_size or self.MAX_WORDS_SIZE):
             context.log(f"Max words reached. Stopping.", self.name)
-            too_long = sheerka.new(BuiltinConcepts.CONCEPT_TOO_LONG, body=parser_input)
-            body = sheerka.new(BuiltinConcepts.NOT_FOR_ME, body=parser_input, reason=too_long)
+            too_long = sheerka.new(BuiltinConcepts.CONCEPT_TOO_LONG, body=parser_input.as_text())
+            body = sheerka.new(BuiltinConcepts.NOT_FOR_ME, body=parser_input.as_text(), reason=too_long)
             return sheerka.ret(self.name, False, body)
 
         already_recognized = []  # keep track of the concepts founds
@@ -78,12 +80,13 @@ class ExactConceptParser(BaseParser):
 
                 already_recognized.append(concept)
 
-        by_name = sheerka.resolve(self.get_input_as_text(parser_input))
+        by_name = sheerka.resolve(parser_input.as_text())
         core.builtin_helpers.set_is_evaluated(by_name)
         recognized = self.merge_concepts(already_recognized, by_name)
 
         if len(recognized) == 0:
-            ret = sheerka.ret(self.name, False, sheerka.new(BuiltinConcepts.UNKNOWN_CONCEPT, body=parser_input))
+            ret = sheerka.ret(self.name, False, sheerka.new(BuiltinConcepts.UNKNOWN_CONCEPT,
+                                                            body=parser_input.as_text()))
             self.log_result(context, parser_input, ret)
             return ret
         else:
@@ -94,10 +97,10 @@ class ExactConceptParser(BaseParser):
                 self.log_multiple_results(context, parser_input, res)
             return res
 
-    def get_words(self, text):
-        tokens = self.get_input_as_tokens(text)
+    @staticmethod
+    def get_words(parser_input):
         res = []
-        for t in tokens:
+        for t in parser_input.as_tokens():
             if t.type == TokenKind.EOF:
                 break
             if t.type == TokenKind.NEWLINE or t.type == TokenKind.WHITESPACE:
@@ -173,6 +176,6 @@ class ExactConceptParser(BaseParser):
             context.sheerka.new(
                 BuiltinConcepts.PARSER_RESULT,
                 parser=self,
-                source=parser_input if isinstance(parser_input, str) else self.get_text_from_tokens(parser_input),
+                source=parser_input.as_text(),
                 body=concept,
                 try_parsed=concept))
diff --git a/src/parsers/PythonParser.py b/src/parsers/PythonParser.py
index ffa717d..1f652a5 100644
--- a/src/parsers/PythonParser.py
+++ b/src/parsers/PythonParser.py
@@ -4,6 +4,7 @@ from dataclasses import dataclass
 
 import core.utils
 from core.builtin_concepts import BuiltinConcepts
+from core.sheerka.services.SheerkaExecute import ParserInput, SheerkaExecute
 from core.tokenizer import LexerError, TokenKind
 from parsers.BaseParser import BaseParser, Node, ErrorNode
 from parsers.BnfNodeParser import ConceptNode
@@ -28,7 +29,7 @@ class PythonNode(Node):
         self.concepts = concepts or {}  # when concepts are recognized in the expression
 
     # def __repr__(self):
-    #     return "PythonNode(source='" + self.source + "', ast=" + self.get_dump(self.ast_) + ")"
+    #     return "PythonNode(parser_input='" + self.parser_input + "', ast=" + self.get_dump(self.ast_) + ")"
 
     def __repr__(self):
         ast_type = "expr" if isinstance(self.ast_, ast.Expression) else "module"
@@ -57,77 +58,6 @@ class PythonNode(Node):
         return dump
 
 
-class PythonParser(BaseParser):
-    """
-    Parse Python scripts
-    """
-
-    def __init__(self, **kwargs):
-
-        BaseParser.__init__(self, "Python", 50)
-        self.source = kwargs.get("source", "<undef>")
-
-    def parse(self, context, parser_input):
-        sheerka = context.sheerka
-        tree = None
-
-        python_switcher = {
-            TokenKind.CONCEPT: lambda t: core.utils.encode_concept(t.value)
-        }
-
-        try:
-            tracker = {}
-            source = self.get_input_as_text(parser_input, python_switcher, tracker)
-            source = source.strip()
-            parser_input = parser_input if isinstance(parser_input, str) else source
-
-            #  first, try to parse an expression
-            res, tree, error = self.try_parse_expression(source)
-            if not res:
-                # then try to parse a statement
-                res, tree, error = self.try_parse_statement(source)
-                if not res:
-                    error_node = PythonErrorNode(parser_input, error)
-                    self.error_sink.append(error_node)
-
-        except LexerError as e:
-            self.error_sink.append(e)
-
-        if self.has_error:
-            ret = sheerka.ret(
-                self.name,
-                False,
-                sheerka.new(
-                    BuiltinConcepts.NOT_FOR_ME,
-                    body=parser_input,
-                    reason=self.error_sink))
-        else:
-            ret = sheerka.ret(
-                self.name,
-                True,
-                sheerka.new(
-                    BuiltinConcepts.PARSER_RESULT,
-                    parser=self,
-                    source=parser_input,
-                    body=PythonNode(parser_input, tree, tracker),
-                    try_parsed=None))
-
-        self.log_result(context, parser_input, ret)
-        return ret
-
-    def try_parse_expression(self, text):
-        try:
-            return True, ast.parse(text, f"<{self.source}>", 'eval'), None
-        except Exception as error:
-            return False, None, error
-
-    def try_parse_statement(self, text):
-        try:
-            return True, ast.parse(text, f"<{self.source}>", 'exec'), None
-        except Exception as error:
-            return False, None, error
-
-
 class PythonGetNamesVisitor(ast.NodeVisitor):
     """
     This visitor will find all the name declared in the ast
@@ -206,7 +136,8 @@ class LexerNodeParserHelperForPython:
         with context.push(self, desc="Trying Python for '" + to_parse + "'") as sub_context:
             sub_context.add_inputs(to_parse=to_parse)
             python_parser = PythonParser()
-            result = python_parser.parse(sub_context, to_parse)
+            parser_input = context.sheerka.services[SheerkaExecute.NAME].get_parser_input(to_parse)
+            result = python_parser.parse(sub_context, parser_input)
             sub_context.add_values(return_values=result)
 
         if result.status:
@@ -216,3 +147,75 @@ class LexerNodeParserHelperForPython:
             return python_node
 
         return result.body  # the error
+
+
+class PythonParser(BaseParser):
+    """
+    Parse Python scripts
+    """
+
+    def __init__(self, **kwargs):
+
+        BaseParser.__init__(self, "Python", 50)
+        self.source = kwargs.get("source", "<undef>")
+
+    def parse(self, context, parser_input: ParserInput):
+        sheerka = context.sheerka
+        tree = None
+        tracker = {}  # to keep track of concept tokens (c:xxx:)
+
+        python_switcher = {
+            TokenKind.CONCEPT: lambda t: core.utils.encode_concept(t.value)
+        }
+
+        try:
+            parser_input.reset()
+
+            source_code = parser_input.as_text(python_switcher, tracker)
+            source_code = source_code.strip()
+
+            #  first, try to parse an expression
+            res, tree, error = self.try_parse_expression(source_code)
+            if not res:
+                # then try to parse a statement
+                res, tree, error = self.try_parse_statement(source_code)
+                if not res:
+                    error_node = PythonErrorNode(parser_input.as_text(), error)
+                    self.error_sink.append(error_node)
+
+        except LexerError as e:
+            self.error_sink.append(e)
+
+        if self.has_error:
+            ret = sheerka.ret(
+                self.name,
+                False,
+                sheerka.new(
+                    BuiltinConcepts.NOT_FOR_ME,
+                    body=parser_input.as_text(),
+                    reason=self.error_sink))
+        else:
+            ret = sheerka.ret(
+                self.name,
+                True,
+                sheerka.new(
+                    BuiltinConcepts.PARSER_RESULT,
+                    parser=self,
+                    source=parser_input.as_text(),
+                    body=PythonNode(source_code, tree, tracker),
+                    try_parsed=None))
+
+        self.log_result(context, parser_input.as_text(), ret)
+        return ret
+
+    def try_parse_expression(self, text):
+        try:
+            return True, ast.parse(text, f"<{self.source}>", 'eval'), None
+        except Exception as error:
+            return False, None, error
+
+    def try_parse_statement(self, text):
+        try:
+            return True, ast.parse(text, f"<{self.source}>", 'exec'), None
+        except Exception as error:
+            return False, None, error
diff --git a/src/parsers/PythonWithConceptsParser.py b/src/parsers/PythonWithConceptsParser.py
index 52b939a..92dc4f9 100644
--- a/src/parsers/PythonWithConceptsParser.py
+++ b/src/parsers/PythonWithConceptsParser.py
@@ -1,4 +1,5 @@
 from core.builtin_concepts import BuiltinConcepts
+from core.sheerka.services.SheerkaExecute import SheerkaExecute
 from parsers.BaseParser import BaseParser
 from parsers.BnfNodeParser import ConceptNode
 from parsers.PythonParser import PythonParser
@@ -77,8 +78,9 @@ class PythonWithConceptsParser(BaseParser):
                 to_parse += node.source
 
         with context.push(self, "Trying Python for '" + to_parse + "'") as sub_context:
+            parser_input = context.sheerka.services[SheerkaExecute.NAME].get_parser_input(to_parse)
             python_parser = PythonParser()
-            result = python_parser.parse(sub_context, to_parse)
+            result = python_parser.parse(sub_context, parser_input)
 
         if result.status:
             python_node = result.body.body
diff --git a/src/parsers/SyaNodeParser.py b/src/parsers/SyaNodeParser.py
index d81c70d..ed8ebeb 100644
--- a/src/parsers/SyaNodeParser.py
+++ b/src/parsers/SyaNodeParser.py
@@ -6,7 +6,7 @@ from typing import List
 from core import builtin_helpers
 from core.builtin_concepts import BuiltinConcepts
 from core.concept import Concept, DEFINITION_TYPE_BNF
-from core.sheerka.ExecutionContext import ExecutionContext
+from core.sheerka.services.SheerkaExecute import ParserInput
 from core.tokenizer import Token, TokenKind, Tokenizer
 from parsers.BaseNodeParser import UnrecognizedTokensNode, ConceptNode, SourceCodeNode, SyaAssociativity, \
     SourceCodeWithConceptNode, BaseNodeParser
@@ -313,21 +313,6 @@ class InFixToPostFix:
         """
         return len(self.stack) > 0 and isinstance(self.stack[-1], type)
 
-    def _get_lexer_nodes_from_unrecognized(self):
-        """
-        Use the source of self.unrecognized_tokens gto find concepts or source code
-        :return:
-        """
-
-        res = builtin_helpers.parse_unrecognized(self.context, self.unrecognized_tokens.source, PARSERS)
-        only_parsers_results = builtin_helpers.only_parsers_results(self.context, res)
-        if not only_parsers_results.status:
-            return None
-
-        return builtin_helpers.get_lexer_nodes(
-            only_parsers_results.body.body,
-            self.unrecognized_tokens.start,
-            self.unrecognized_tokens.tokens)
 
     def _make_source_code_with_concept(self, start, rpar_token, end):
         """
@@ -440,7 +425,10 @@ class InFixToPostFix:
         self.unrecognized_tokens.fix_source()
 
         # try to recognize concepts
-        nodes_sequences = self._get_lexer_nodes_from_unrecognized()
+        nodes_sequences = builtin_helpers.get_lexer_nodes_from_unrecognized(
+            self.context,
+            self.unrecognized_tokens,
+            PARSERS)
 
         if nodes_sequences:
             # There are more than one solution found
@@ -482,7 +470,10 @@ class InFixToPostFix:
         :return: list of function_parser_res
         """
         self.unrecognized_tokens.fix_source()
-        nodes_sequences = self._get_lexer_nodes_from_unrecognized()
+        nodes_sequences = builtin_helpers.get_lexer_nodes_from_unrecognized(
+            self.context,
+            self.unrecognized_tokens,
+            PARSERS)
         if nodes_sequences is None:
             return None
 
@@ -908,13 +899,13 @@ class SyaNodeParser(BaseNodeParser):
             self.concepts_by_first_keyword = {}
             self.sya_definitions = {}
 
-        self.token = None
-        self.pos = -1
-        self.tokens = None
-
-        self.context: ExecutionContext = None
-        self.text = None
-        self.sheerka = None
+        # self.token = None
+        # self.pos = -1
+        # self.tokens = None
+        #
+        # self.context: ExecutionContext = None
+        # self.text = None
+        # self.sheerka = None
 
     def init_from_concepts(self, context, concepts, **kwargs):
         super().init_from_concepts(context, concepts)
@@ -954,15 +945,15 @@ class SyaNodeParser(BaseNodeParser):
 
         return sya_concept_def
 
-    def infix_to_postfix(self, context, text):
+    def infix_to_postfix(self, context, parser_input: ParserInput):
         """
         Implementing Shunting Yard Algorithm
         :param context:
-        :param text:
+        :param parser_input:
         :return:
         """
 
-        if not self.reset_parser(context, text):
+        if not self.reset_parser(context, parser_input):
             return None
 
         forked = []
@@ -978,32 +969,32 @@ class SyaNodeParser(BaseNodeParser):
                 forked.clear()
 
         res = [InFixToPostFix(context)]
-        while self.next_token(False):
+        while self.parser_input.next_token(False):
             for infix_to_postfix in res:
                 infix_to_postfix.reset()
 
-            token = self.get_token()
+            token = self.parser_input.token
 
             try:
                 if token.type in (TokenKind.LPAR, TokenKind.RPAR):
                     # little optim, no need to lock, unlock or get the concept when parenthesis
                     for infix_to_postfix in res:
-                        infix_to_postfix.eat_token(token, self.pos)
+                        infix_to_postfix.eat_token(token, self.parser_input.pos)
                     continue
 
                 for infix_to_postfix in res:
-                    if infix_to_postfix.eat_token(token, self.pos):
+                    if infix_to_postfix.eat_token(token, self.parser_input.pos):
                         infix_to_postfix.lock()
 
                 concepts = self.get_concepts(token, self._is_eligible, to_map=self._get_sya_concept_def)
                 if not concepts:
                     for infix_to_postfix in res:
-                        infix_to_postfix.eat_unrecognized(token, self.pos)
+                        infix_to_postfix.eat_unrecognized(token, self.parser_input.pos)
                     continue
 
                 if len(concepts) == 1:
                     for infix_to_postfix in res:
-                        infix_to_postfix.eat_concept(concepts[0], token, self.pos)
+                        infix_to_postfix.eat_concept(concepts[0], token, self.parser_input.pos)
                     continue
 
                 # make the cartesian product
@@ -1012,7 +1003,7 @@ class SyaNodeParser(BaseNodeParser):
                     for concept in concepts:
                         clone = infix_to_postfix.clone()
                         temp_res.append(clone)
-                        clone.eat_concept(concept, token, self.pos)
+                        clone.eat_concept(concept, token, self.parser_input.pos)
                 res = temp_res
 
             finally:
@@ -1036,14 +1027,15 @@ class SyaNodeParser(BaseNodeParser):
             while len(item.nodes) > 0:
                 res = self.postfix_to_item(sheerka, item.nodes)
                 if isinstance(res, PostFixToItem):
-                    items.append(ConceptNode(res.concept, res.start, res.end, self.tokens[res.start: res.end + 1]))
+                    items.append(
+                        ConceptNode(res.concept, res.start, res.end, self.parser_input.tokens[res.start: res.end + 1]))
                 else:
                     items.append(res)
                 item.has_unrecognized |= hasattr(res, "has_unrecognized") and res.has_unrecognized or \
                                          isinstance(res, UnrecognizedTokensNode)
             item.nodes = items
             item.fix_all_pos()
-            item.tokens = self.tokens[item.start:item.end + 1]
+            item.tokens = self.parser_input.tokens[item.start:item.end + 1]
             item.fix_source(True)
             return item
 
@@ -1069,14 +1061,14 @@ class SyaNodeParser(BaseNodeParser):
 
         return PostFixToItem(concept, start, end, has_unrecognized)
 
-    def parse(self, context, parser_input):
+    def parse(self, context, parser_input: ParserInput):
         """
 
         :param context:
         :param parser_input:
         :return:
         """
-        if parser_input == "":
+        if parser_input.is_empty():
             return context.sheerka.ret(
                 self.name,
                 False,
@@ -1096,7 +1088,7 @@ class SyaNodeParser(BaseNodeParser):
             return self.sheerka.ret(
                 self.name,
                 False,
-                context.sheerka.new(BuiltinConcepts.NOT_FOR_ME, body=parser_input))
+                context.sheerka.new(BuiltinConcepts.NOT_FOR_ME, body=parser_input.as_text()))
 
         for infix_to_postfix in valid_infix_to_postfixs:
             sequence = []
@@ -1106,7 +1098,10 @@ class SyaNodeParser(BaseNodeParser):
                 has_unrecognized |= hasattr(item, "has_unrecognized") and item.has_unrecognized or \
                                     isinstance(item, UnrecognizedTokensNode)
                 if isinstance(item, PostFixToItem):
-                    to_insert = ConceptNode(item.concept, item.start, item.end, self.tokens[item.start: item.end + 1])
+                    to_insert = ConceptNode(item.concept,
+                                            item.start,
+                                            item.end,
+                                            self.parser_input.tokens[item.start: item.end + 1])
                 else:
                     to_insert = item
                 sequence.insert(0, to_insert)
diff --git a/src/parsers/UnrecognizedNodeParser.py b/src/parsers/UnrecognizedNodeParser.py
index cb89979..0d1f397 100644
--- a/src/parsers/UnrecognizedNodeParser.py
+++ b/src/parsers/UnrecognizedNodeParser.py
@@ -109,7 +109,7 @@ class UnrecognizedNodeParser(BaseParser):
                     _validate_concept(value)
 
                 elif isinstance(value, UnrecognizedTokensNode):
-                    res = parse_unrecognized(context, value.tokens, PARSERS)
+                    res = parse_unrecognized(context, value.source, PARSERS)
                     res = only_successful(context, res)  # only key successful parsers
                     if res.status:
                         concept.compiled[name] = res.body.body
diff --git a/src/sheerkapickle/SheerkaPickler.py b/src/sheerkapickle/SheerkaPickler.py
index 33e04f3..3bcec93 100644
--- a/src/sheerkapickle/SheerkaPickler.py
+++ b/src/sheerkapickle/SheerkaPickler.py
@@ -3,6 +3,7 @@ from logging import Logger
 
 import core.utils
 from core.concept import Concept
+from core.sheerka.services.SheerkaExecute import ParserInput
 
 from sheerkapickle import utils, tags, handlers
 
@@ -37,6 +38,7 @@ class SheerkaPickler:
         from parsers.BaseParser import BaseParser
         from evaluators.BaseEvaluator import BaseEvaluator
         self.to_reduce.append(ToReduce(lambda o: isinstance(o, (BaseParser, BaseEvaluator)), lambda o: o.name))
+        self.to_reduce.append(ToReduce(lambda o: isinstance(o, ParserInput), lambda o: o.as_text()))
 
     def flatten(self, obj):
         if utils.is_primitive(obj):
diff --git a/src/sheerkapickle/sheerka_handlers.py b/src/sheerkapickle/sheerka_handlers.py
index 188c0e2..a3f41c6 100644
--- a/src/sheerkapickle/sheerka_handlers.py
+++ b/src/sheerkapickle/sheerka_handlers.py
@@ -1,5 +1,6 @@
 from core.builtin_concepts import UserInputConcept, ReturnValueConcept, BuiltinConcepts
 from core.sheerka.Sheerka import Sheerka
+from core.sheerka.services.SheerkaExecute import ParserInput
 from evaluators.BaseEvaluator import BaseEvaluator
 from parsers.BaseParser import BaseParser
 from sheerkapickle.handlers import BaseHandler, registry
@@ -79,7 +80,9 @@ class UserInputHandler(ConceptHandler):
     def flatten(self, obj: UserInputConcept, data):
         data[CONCEPT_ID] = (obj.key, obj.id)
         data["user_name"] = obj.user_name
-        data["text"] = BaseParser.get_text_from_tokens(obj.text) if isinstance(obj.text, list) else obj.text
+        data["text"] = BaseParser.get_text_from_tokens(obj.text) if isinstance(obj.text, list) else \
+            obj.text.as_text() if isinstance(obj.text, ParserInput) else \
+            obj.text
         return data
 
     def new(self, data):
diff --git a/tests/BaseTest.py b/tests/BaseTest.py
index 0de2842..ec5a473 100644
--- a/tests/BaseTest.py
+++ b/tests/BaseTest.py
@@ -24,10 +24,10 @@ class BaseTest:
     def get_default_concept(self):
         concept = Concept(
             name="a + b",
-            where="isinstance(a, int) and isinstance(b, int)",
-            pre="isinstance(a, int) and isinstance(b, int)",
-            post="isinstance(res, int)",
-            body="def func(x,y):\n    return x+y\nfunc(a,b)",
+            where="isinstance(a, int) and isinstance(b, int)\n",
+            pre="isinstance(a, int) and isinstance(b, int)\n",
+            post="isinstance(res, int)\n",
+            body="def func(x,y):\n    return x+y\nfunc(a,b)\n",
             desc="specific description")
         concept.def_var("a", "value1")
         concept.def_var("b", "value2")
diff --git a/tests/core/test_ParserInput.py b/tests/core/test_ParserInput.py
new file mode 100644
index 0000000..81cdd5d
--- /dev/null
+++ b/tests/core/test_ParserInput.py
@@ -0,0 +1,79 @@
+import pytest
+from core.sheerka.services.SheerkaExecute import ParserInput
+from core.tokenizer import Tokenizer
+
+
+@pytest.mark.parametrize("text, start, end, expected", [
+    ("def concept a", None, None, "def concept a"),
+    ("&é#(-è_çà)='string'", None, None, "&é#(-è_çà)='string'"),
+    ("def concept a", 2, None, "concept a"),
+    ("def concept a", 0, 2, "def concept"),
+])
+def test_i_can_use_parser_input(text, start, end, expected):
+    parser_input = ParserInput(text, start=start, end=end).reset()
+    assert parser_input.as_text() == expected
+
+
+def test_i_can_get_the_next_token():
+    parser_input = ParserInput("def concept a from bnf 'xyz' as 'xyz'").reset()
+    res = []
+    while parser_input.next_token():
+        res.append(f"{parser_input.token.str_value}")
+
+    assert res == ['def', 'concept', 'a', 'from', 'bnf', "'xyz'", 'as', "'xyz'", '']
+
+    parser_input = ParserInput("def concept a concept name from bnf 'xyz' as 'xyz'", start=4, end=9).reset()
+    res = []
+    while parser_input.next_token(skip_whitespace=False):
+        res.append(f"{parser_input.token.str_value}")
+
+    assert res == ['a', ' ', 'concept', ' ', 'name', ' ']
+
+
+def test_i_can_get_the_next_token_when_initialised_with_tokens():
+    tokens = list(Tokenizer(" def concept a as 'xyz' "))
+    parser_input = ParserInput(" def concept a as 'xyz' ", tokens).reset()
+    res = []
+    while parser_input.next_token():
+        res.append(f"{parser_input.token.str_value}")
+
+    assert res == ['def', 'concept', 'a', 'as', "'xyz'", '']
+
+    tokens = list(Tokenizer(" def concept a as 'xyz' ", yield_eof=False))
+    parser_input = ParserInput(" def concept a as 'xyz' ", tokens).reset()
+    res = []
+    while parser_input.next_token():
+        res.append(f"{parser_input.token.str_value}")
+
+    assert res == ['def', 'concept', 'a', 'as', "'xyz'"]
+
+
+def test_i_can_parse_twice():
+    text = """
+    def concept a + b
+    where isinstance(a, int) and isinstance(b, int)
+    pre isinstance(a, int) and isinstance(b, int)
+    post isinstance(res, int)
+    as:
+        def func(x,y):
+            return x+y
+        func(a,b)
+                """
+
+    p1 = ParserInput(text).reset()
+    while p1.next_token():
+        pass
+
+    p1.reset()
+    p2 = ParserInput(text).reset()
+
+    while p1.next_token():
+        p2.next_token()
+        assert p1.token == p2.token
+
+    p1.reset()
+    p2 = ParserInput(text).reset()
+
+    while p2.next_token():
+        p1.next_token()
+        assert p1.token == p2.token
diff --git a/tests/core/test_sheerka_call_parsers.py b/tests/core/test_sheerka_call_parsers.py
index 71ef47d..dfae9b3 100644
--- a/tests/core/test_sheerka_call_parsers.py
+++ b/tests/core/test_sheerka_call_parsers.py
@@ -1,4 +1,5 @@
 from core.builtin_concepts import ReturnValueConcept, UserInputConcept, BuiltinConcepts, ParserResultConcept
+from core.sheerka.services.SheerkaExecute import ParserInput
 from parsers.BaseParser import BaseParser
 
 from tests.TestUsingMemoryBasedSheerka import TestUsingMemoryBasedSheerka
@@ -22,7 +23,7 @@ class BaseTestParser(BaseParser):
 
     @staticmethod
     def _get_source(text_):
-        return text_ if isinstance(text_, str) else text_.body
+        return text_.as_text() if isinstance(text_, ParserInput) else text_.body
 
     def _out(self, name, priority, status, source):
         debug = f"name={name}"
@@ -33,7 +34,7 @@ class BaseTestParser(BaseParser):
 
     def parse(self, context, text):
         self._out(self._get_name(self.name), self.priority, self.status, self._get_source(text))
-        value = self._get_name(self.name) + ":" + (text if isinstance(text, str) else text.body)
+        value = self._get_name(self.name) + ":" + self._get_source(text)
         parser_result = ParserResultConcept(parser=self, value=value)
         return ReturnValueConcept(self, self.status, self.parser_result or parser_result)
 
@@ -54,8 +55,8 @@ class Enabled80MultipleFalseParser(BaseTestParser):
 
     def parse(self, context, text):
         self._out(self._get_name(self.name), self.priority, self.status, self._get_source(text))
-        value1 = self._get_name(self.name) + ":" + (text if isinstance(text, str) else text.body) + "_1"
-        value2 = self._get_name(self.name) + ":" + (text if isinstance(text, str) else text.body) + "_2"
+        value1 = self._get_name(self.name) + ":" + self._get_source(text) + "_1"
+        value2 = self._get_name(self.name) + ":" + self._get_source(text) + "_2"
         return [
             ReturnValueConcept(self, self.status, ParserResultConcept(parser=self, value=value1)),
             ReturnValueConcept(self, self.status, ParserResultConcept(parser=self, value=value2)),
@@ -68,8 +69,8 @@ class Enabled80MultipleTrueParser(BaseTestParser):
 
     def parse(self, context, text):
         self._out(self._get_name(self.name), self.priority, self.status, self._get_source(text))
-        value1 = self._get_name(self.name) + ":" + (text if isinstance(text, str) else text.body) + "_1"
-        value2 = self._get_name(self.name) + ":" + (text if isinstance(text, str) else text.body) + "_2"
+        value1 = self._get_name(self.name) + ":" + self._get_source(text) + "_1"
+        value2 = self._get_name(self.name) + ":" + self._get_source(text) + "_2"
         return [
             ReturnValueConcept(self, True, ParserResultConcept(parser=self, value=value1)),
             ReturnValueConcept(self, False, ParserResultConcept(parser=self, value=value2)),
@@ -90,7 +91,7 @@ class Enabled50TrueParser(BaseTestParser):
         status = isinstance(text, ParserResultConcept) and source == "Enabled80False:Enabled90False:hello world"
         self._out(self._get_name(self.name), self.priority, status, source)
 
-        value = self._get_name(self.name) + ":" + (text if isinstance(text, str) else text.body)
+        value = self._get_name(self.name) + ":" + self._get_source(text)
         return_value = ParserResultConcept(parser=self, value=value)
         return ReturnValueConcept(self, status, return_value)
 
diff --git a/tests/evaluators/test_LexerNodeEvaluator.py b/tests/evaluators/test_LexerNodeEvaluator.py
index 3e4ed7a..7850970 100644
--- a/tests/evaluators/test_LexerNodeEvaluator.py
+++ b/tests/evaluators/test_LexerNodeEvaluator.py
@@ -3,6 +3,7 @@ import ast
 import pytest
 from core.builtin_concepts import ReturnValueConcept, ParserResultConcept, BuiltinConcepts
 from core.concept import Concept, ConceptParts, DoNotResolve
+from core.sheerka.services.SheerkaExecute import ParserInput
 from evaluators.LexerNodeEvaluator import LexerNodeEvaluator
 from parsers.BaseNodeParser import SourceCodeNode
 from parsers.BnfNodeParser import ConceptNode, BnfNodeParser, UnrecognizedTokensNode
@@ -17,7 +18,7 @@ class TestLexerNodeEvaluator(TestUsingMemoryBasedSheerka):
         parser = BnfNodeParser()
         parser.init_from_concepts(context, concepts)
 
-        ret_val = parser.parse(context, expression)
+        ret_val = parser.parse(context, ParserInput(expression))
         assert ret_val.status
         return ret_val
 
diff --git a/tests/evaluators/test_PythonEvaluator.py b/tests/evaluators/test_PythonEvaluator.py
index ba5c6b0..f4be56d 100644
--- a/tests/evaluators/test_PythonEvaluator.py
+++ b/tests/evaluators/test_PythonEvaluator.py
@@ -2,6 +2,7 @@ import pytest
 
 from core.builtin_concepts import ReturnValueConcept, ParserResultConcept, BuiltinConcepts
 from core.concept import Concept, DEFINITION_TYPE_DEF
+from core.sheerka.services.SheerkaExecute import ParserInput
 from evaluators.PythonEvaluator import PythonEvaluator
 from parsers.PythonParser import PythonNode, PythonParser
 from tests.TestUsingMemoryBasedSheerka import TestUsingMemoryBasedSheerka
@@ -31,7 +32,7 @@ class TestPythonEvaluator(TestUsingMemoryBasedSheerka):
     ])
     def test_i_can_eval(self, text, expected):
         context = self.get_context()
-        parsed = PythonParser().parse(context, text)
+        parsed = PythonParser().parse(context, ParserInput(text))
 
         evaluated = PythonEvaluator().eval(context, parsed)
 
@@ -40,7 +41,7 @@ class TestPythonEvaluator(TestUsingMemoryBasedSheerka):
 
     def test_i_can_eval_using_context(self):
         context = self.get_context()
-        parsed = PythonParser().parse(context, "test_using_context('value for param1', 10)")
+        parsed = PythonParser().parse(context, ParserInput("test_using_context('value for param1', 10)"))
 
         evaluated = PythonEvaluator().eval(context, parsed)
 
@@ -49,7 +50,7 @@ class TestPythonEvaluator(TestUsingMemoryBasedSheerka):
 
     def test_i_can_eval_using_context_when_self_is_not_sheerka(self):
         sheerka, context = self.init_concepts()
-        parsed = PythonParser().parse(context, "create_new_concept(Concept('foo'))")
+        parsed = PythonParser().parse(context, ParserInput("create_new_concept(Concept('foo'))"))
 
         evaluated = PythonEvaluator().eval(context, parsed)
 
@@ -66,7 +67,7 @@ class TestPythonEvaluator(TestUsingMemoryBasedSheerka):
         context = self.get_context()
         context.sheerka.add_in_cache(Concept("foo"))
 
-        parsed = PythonParser().parse(context, "foo")
+        parsed = PythonParser().parse(context, ParserInput("foo"))
         evaluated = PythonEvaluator().eval(context, parsed)
 
         assert not evaluated.status
@@ -80,7 +81,7 @@ class TestPythonEvaluator(TestUsingMemoryBasedSheerka):
         context = self.get_context()
         context.sheerka.add_in_cache(Concept("foo", body="1"))
 
-        parsed = PythonParser().parse(context, "foo + 2")
+        parsed = PythonParser().parse(context, ParserInput("foo + 2"))
         evaluated = PythonEvaluator().eval(context, parsed)
 
         assert evaluated.status
@@ -94,7 +95,7 @@ class TestPythonEvaluator(TestUsingMemoryBasedSheerka):
         context = self.get_context()
         context.sheerka.add_in_cache(Concept("foo"))
 
-        parsed = PythonParser().parse(context, "def a(b):\n    return b\na(c:foo:)")
+        parsed = PythonParser().parse(context, ParserInput("def a(b):\n    return b\na(c:foo:)"))
         evaluated = PythonEvaluator().eval(context, parsed)
 
         assert evaluated.status
@@ -108,7 +109,7 @@ class TestPythonEvaluator(TestUsingMemoryBasedSheerka):
         context = self.get_context()
         context.sheerka.add_in_cache(Concept("foo", body="2"))
 
-        parsed = PythonParser().parse(context, "def a(b):\n    return b\na(foo)")
+        parsed = PythonParser().parse(context, ParserInput("def a(b):\n    return b\na(foo)"))
         evaluated = PythonEvaluator().eval(context, parsed)
 
         assert evaluated.status
@@ -118,7 +119,7 @@ class TestPythonEvaluator(TestUsingMemoryBasedSheerka):
         context = self.get_context()
         context.sheerka.add_in_cache(Concept("foo", body="2"))
 
-        parsed = PythonParser().parse(context, "get_concept_name(c:foo:)")
+        parsed = PythonParser().parse(context, ParserInput("get_concept_name(c:foo:)"))
         python_evaluator = PythonEvaluator()
         python_evaluator.locals["get_concept_name"] = get_concept_name
         evaluated = python_evaluator.eval(context, parsed)
@@ -127,7 +128,7 @@ class TestPythonEvaluator(TestUsingMemoryBasedSheerka):
         assert evaluated.value == "foo"
 
         # sanity, does not work otherwise
-        parsed = PythonParser().parse(context, "get_concept_name(foo)")
+        parsed = PythonParser().parse(context, ParserInput("get_concept_name(foo)"))
         python_evaluator = PythonEvaluator()
         python_evaluator.locals["get_concept_name"] = get_concept_name
         evaluated = python_evaluator.eval(context, parsed)
@@ -141,7 +142,7 @@ class TestPythonEvaluator(TestUsingMemoryBasedSheerka):
             self.from_def_concept("mult", "a mult b", ["a", "b"]),
         )
 
-        parsed = PythonParser().parse(context, "is_greater_than(BuiltinConcepts.PRECEDENCE, mult, plus)")
+        parsed = PythonParser().parse(context, ParserInput("is_greater_than(BuiltinConcepts.PRECEDENCE, mult, plus)"))
         python_evaluator = PythonEvaluator()
 
         evaluated = python_evaluator.eval(context, parsed)
diff --git a/tests/non_reg/test_sheerka_non_reg.py b/tests/non_reg/test_sheerka_non_reg.py
index 451923b..6a16e25 100644
--- a/tests/non_reg/test_sheerka_non_reg.py
+++ b/tests/non_reg/test_sheerka_non_reg.py
@@ -100,7 +100,7 @@ as:
     def func(x,y):
         return x+y
     func(a,b)
-        """
+"""
 
         expected = self.get_default_concept()
         expected.metadata.id = "1001"
@@ -167,7 +167,7 @@ as:
     def func(x,y):
         return x+y
     func(a,b)
-            """
+"""
 
         sheerka = self.get_sheerka()
         sheerka.evaluate_user_input(text)
diff --git a/tests/parsers/test_AtomsParser.py b/tests/parsers/test_AtomsParser.py
index 4d95668..1c91284 100644
--- a/tests/parsers/test_AtomsParser.py
+++ b/tests/parsers/test_AtomsParser.py
@@ -1,6 +1,7 @@
 import pytest
 from core.builtin_concepts import BuiltinConcepts
 from core.concept import Concept, DEFINITION_TYPE_DEF
+from core.sheerka.services.SheerkaExecute import ParserInput
 from parsers.AtomNodeParser import AtomNodeParser
 from parsers.BaseNodeParser import cnode, utnode, CNC, SCN, CN
 
@@ -26,7 +27,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
     def test_i_cannot_parse_empty_string(self):
         sheerka, context, parser = self.init_parser({})
 
-        res = parser.parse(context, "")
+        res = parser.parse(context, ParserInput(""))
 
         assert not res.status
         assert sheerka.isinstance(res.body, BuiltinConcepts.IS_EMPTY)
@@ -49,7 +50,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
         }
 
         sheerka, context, parser = self.init_parser(concepts_map, create_new=True, use_sheerka=True)
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         wrapper = res.body
         lexer_nodes = res.body.body
 
@@ -72,7 +73,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
         }
 
         sheerka, context, parser = self.init_parser(concepts_map)
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         wrapper = res.body
         lexer_nodes = res.body.body
 
@@ -110,7 +111,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
         }
 
         sheerka, context, parser = self.init_parser(concepts_map)
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         wrapper = res.body
         lexer_nodes = res.body.body
 
@@ -137,7 +138,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
         }
 
         sheerka, context, parser = self.init_parser(concepts_map)
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         wrapper = res.body
         lexer_nodes = res.body.body
 
@@ -158,7 +159,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
         }
 
         sheerka, context, parser = self.init_parser(concepts_map)
-        list_of_res = parser.parse(context, text)
+        list_of_res = parser.parse(context, ParserInput(text))
         assert len(list_of_res) == len(expected)
 
         for i, res in enumerate(list_of_res):
@@ -180,7 +181,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
 
         text = "one two x$!# one two"
         sheerka, context, parser = self.init_parser(concepts_map)
-        list_of_res = parser.parse(context, text)
+        list_of_res = parser.parse(context, ParserInput(text))
 
         expected = [
             (False, ["one", "two", " x$!# ", ("one", 1), ("two", 1)]),
@@ -210,7 +211,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser(concepts_map)
         sheerka.set_isa(context, sheerka.new("one"), sheerka.new("number"))
 
-        res = parser.parse(context, "one")
+        res = parser.parse(context, ParserInput("one"))
         lexer_nodes = res.body.body
         expected_array = compute_expected_array(concepts_map, "one", ["one"])
         assert lexer_nodes == expected_array
@@ -223,16 +224,36 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
 
         sheerka, context, parser = self.init_parser(concepts_map)
 
-        res = parser.parse(context, "a special concept")
+        res = parser.parse(context, ParserInput("a special concept"))
         lexer_nodes = res.body.body
         expected_array = compute_expected_array(concepts_map, "a special concept", ["a special concept"])
         assert lexer_nodes == expected_array
 
-        res = parser.parse(context, "isa")
+        res = parser.parse(context, ParserInput("isa"))
         lexer_nodes = res.body.body
         expected_array = compute_expected_array(concepts_map, "isa", ["isa"])
         assert lexer_nodes == expected_array
 
+    def test_i_can_parse_concepts_when_sub_tokens(self):
+        concepts_map = {
+            "foo": Concept("foo"),
+            "bar": Concept("bar"),
+        }
+
+        sheerka, context, parser = self.init_parser(concepts_map, create_new=True, use_sheerka=True)
+        text = "not recognized foo bar not not recognized"
+        expected = ["foo", "bar"]
+        parser_input = ParserInput(text, start=3, end=7)
+        res = parser.parse(context, parser_input)
+        wrapper = res.body
+        lexer_nodes = res.body.body
+
+        assert res.status
+
+        expected_array = compute_expected_array(concepts_map, text, expected)
+        assert sheerka.isinstance(wrapper, BuiltinConcepts.PARSER_RESULT)
+        assert lexer_nodes == expected_array
+
     @pytest.mark.parametrize("text", [
         "foo",
         f"foo one",
@@ -249,7 +270,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
         }
 
         sheerka, context, parser = self.init_parser(concepts_map)
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
 
         assert not res.status
         assert sheerka.isinstance(res.body, BuiltinConcepts.NOT_FOR_ME)
@@ -270,7 +291,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
         }
 
         sheerka, context, parser = self.init_parser(concepts_map, create_new=True, singleton=False)
-        list_of_res = parser.parse(context, text)
+        list_of_res = parser.parse(context, ParserInput(text))
 
         assert len(list_of_res) == len(expected)
 
@@ -293,7 +314,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
         }
 
         sheerka, context, parser = self.init_parser(concepts_map)
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         wrapper = res.body
         lexer_nodes = res.body.body
 
@@ -321,7 +342,7 @@ class TestAtomsParser(TestUsingMemoryBasedSheerka):
         }
 
         sheerka, context, parser = self.init_parser(concepts_map, create_new=True, use_sheerka=True)
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         lexer_nodes = res.body.body
 
         assert res.status
diff --git a/tests/parsers/test_BaseParser.py b/tests/parsers/test_BaseParser.py
index 1c21056..e50106e 100644
--- a/tests/parsers/test_BaseParser.py
+++ b/tests/parsers/test_BaseParser.py
@@ -81,3 +81,4 @@ def test_i_can_test_split_iter_parser_indexes():
 ])
 def test_i_can_get_tokens_boundaries(tokens, expected):
     assert BaseParser.get_tokens_boundaries(tokens) == expected
+
diff --git a/tests/parsers/test_BnfNodeParser.py b/tests/parsers/test_BnfNodeParser.py
index 0352673..c2a5401 100644
--- a/tests/parsers/test_BnfNodeParser.py
+++ b/tests/parsers/test_BnfNodeParser.py
@@ -1,6 +1,7 @@
 import pytest
 from core.builtin_concepts import BuiltinConcepts
 from core.concept import Concept, ConceptParts, DoNotResolve, DEFINITION_TYPE_DEF, CC
+from core.sheerka.services.SheerkaExecute import ParserInput
 from parsers.BaseNodeParser import CNC, UTN, CN
 from parsers.BnfNodeParser import BnfNodeParser, StrMatch, TerminalNode, NonTerminalNode, Sequence, OrderedChoice, \
     Optional, ZeroOrMore, OneOrMore, ConceptExpression
@@ -95,7 +96,7 @@ class TestBnfNodeParser(TestUsingMemoryBasedSheerka):
 
         parser = BnfNodeParser()
         parser.init_from_concepts(context, updated)
-        parser.reset_parser(context, text)
+        parser.reset_parser(context, ParserInput(text))
 
         bnf_parsers_helpers = parser.get_concepts_sequences()
 
@@ -113,34 +114,11 @@ class TestBnfNodeParser(TestUsingMemoryBasedSheerka):
             my_map, text, expected, multiple_result, post_init_concepts
         )
         return sequences
-        # sheerka, context, *updated = self.init_concepts(*my_map.values(), create_new=False, singleton=True)
-        # if not multiple_result:
-        #     expected_array = [compute_expected_array(my_map, text, expected)]
-        # else:
-        #     expected_array = [compute_expected_array(my_map, text, e) for e in expected]
-        #
-        # if post_init_concepts:
-        #     post_init_concepts(sheerka, context)
-        #
-        # parser = BnfNodeParser()
-        # parser.init_from_concepts(context, updated)
-        # parser.reset_parser(context, text)
-        #
-        # bnf_parsers_helpers = parser.get_concepts_sequences()
-        #
-        # assert len(bnf_parsers_helpers) == len(expected_array)
-        # for parser_helper, expected_sequence in zip(bnf_parsers_helpers, expected_array):
-        #     assert parser_helper.sequence == expected_sequence
-        #
-        # if len(bnf_parsers_helpers) == 1:
-        #     return bnf_parsers_helpers[0].sequence
-        # else:
-        #     return [pe.sequence for pe in bnf_parsers_helpers]
 
     def test_i_cannot_parse_empty_strings(self):
         sheerka, context, parser = self.init_parser({}, singleton=True)
 
-        res = parser.parse(context, "")
+        res = parser.parse(context, ParserInput(""))
 
         assert not res.status
         assert sheerka.isinstance(res.body, BuiltinConcepts.NOT_FOR_ME)
@@ -738,7 +716,7 @@ class TestBnfNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser(my_map, singleton=True)
         parser.init_from_concepts(context, my_map.values())
 
-        parser.reset_parser(context, "one three")
+        parser.reset_parser(context, ParserInput("one three"))
         sequences = parser.get_concepts_sequences()
         sequence = parser.get_valid(sequences)
 
@@ -756,7 +734,7 @@ class TestBnfNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_can_parse(self, parser_input, expected_status, expected):
         sheerka, context, parser = self.init_parser(init_from_sheerka=True)
 
-        res = parser.parse(context, parser_input)
+        res = parser.parse(context, ParserInput(parser_input))
         expected_array = compute_expected_array(cmap, parser_input, expected)
         parser_result = res.value
         concepts_nodes = res.value.value
@@ -771,7 +749,7 @@ class TestBnfNodeParser(TestUsingMemoryBasedSheerka):
         parser_input = "def one"
         expected = [CNC("def number", source="def one", number="one", one="one")]
 
-        res = parser.parse(context, parser_input)
+        res = parser.parse(context, ParserInput(parser_input))
         expected_array = compute_expected_array(cmap, parser_input, expected)
         expected_array[0].compiled["def"] = cmap["def_only"]
 
diff --git a/tests/parsers/test_BnfParser.py b/tests/parsers/test_BnfParser.py
index 4e9a98b..da2be80 100644
--- a/tests/parsers/test_BnfParser.py
+++ b/tests/parsers/test_BnfParser.py
@@ -1,6 +1,7 @@
 import pytest
 from core.builtin_concepts import BuiltinConcepts
 from core.concept import Concept, DEFINITION_TYPE_BNF
+from core.sheerka.services.SheerkaExecute import ParserInput
 from core.tokenizer import Tokenizer, TokenKind, LexerError, Token
 from parsers.BaseNodeParser import cnode
 from parsers.BaseParser import UnexpectedTokenErrorNode
@@ -135,7 +136,6 @@ class TestBnfParser(TestUsingMemoryBasedSheerka):
         ("1|", UnexpectedEndOfFileError()),
         ("(1|)", UnexpectedTokenErrorNode("Unexpected token 'Token(<EOF>)'", eof_token, [TokenKind.RPAR])),
         ("1=", UnexpectedTokenErrorNode("Unexpected token 'Token(<EOF>)'", eof_token, [TokenKind.IDENTIFIER])),
-        ("'name", LexerError("Missing Trailing quote", "'name", 5, 1, 6))
     ])
     def test_i_can_detect_errors(self, expression, error):
         sheerka, context, parser = self.init_parser()
@@ -146,6 +146,17 @@ class TestBnfParser(TestUsingMemoryBasedSheerka):
         assert not res.status
         assert ret_value[0] == error
 
+    def test_i_can_detect_lexer_error(self):
+        sheerka, context, parser = self.init_parser()
+
+        res = parser.parse(context, Tokenizer("'name"))
+
+        assert not res.status
+        assert sheerka.isinstance(res.body, BuiltinConcepts.ERROR)
+        assert isinstance(res.body.body[0], LexerError)
+        assert res.body.body[0].message == "Missing Trailing quote"
+        assert res.body.body[0].text == "'name"
+
     def test_i_can_use_the_result_of_regex_parsing_to_parse_a_text(self):
         sheerka, context, regex_parser, foo, bar = self.init_parser("foo", "bar")
 
@@ -158,15 +169,15 @@ class TestBnfParser(TestUsingMemoryBasedSheerka):
         bnf_parser = BnfNodeParser()
         bnf_parser.init_from_concepts(context, [foo, bar])
 
-        res = bnf_parser.parse(context, "twenty two")
+        res = bnf_parser.parse(context, ParserInput("twenty two"))
         assert res.status
         assert res.value.body == [cnode("bar", 0, 2, "twenty two")]
 
-        res = bnf_parser.parse(context, "thirty one")
+        res = bnf_parser.parse(context, ParserInput("thirty one"))
         assert res.status
         assert res.value.body == [cnode("bar", 0, 2, "thirty one")]
 
-        res = bnf_parser.parse(context, "twenty")
+        res = bnf_parser.parse(context, ParserInput("twenty"))
         assert res.status
         assert res.value.body == [cnode("foo", 0, 0, "twenty")]
 
diff --git a/tests/parsers/test_DefaultParser.py b/tests/parsers/test_DefaultParser.py
index dc2f5c5..b01d8f0 100644
--- a/tests/parsers/test_DefaultParser.py
+++ b/tests/parsers/test_DefaultParser.py
@@ -1,8 +1,10 @@
 import ast
+from dataclasses import dataclass
 
 import pytest
 from core.builtin_concepts import ParserResultConcept, BuiltinConcepts, ReturnValueConcept
 from core.concept import DEFINITION_TYPE_BNF, DEFINITION_TYPE_DEF
+from core.sheerka.services.SheerkaExecute import ParserInput
 from core.tokenizer import Keywords, Tokenizer, LexerError
 from parsers.BnfNodeParser import OrderedChoice, ConceptExpression, StrMatch
 from parsers.BnfParser import BnfParser
@@ -39,7 +41,7 @@ def get_def_concept(name, where=None, pre=None, post=None, body=None, definition
 
 def get_concept_part(part):
     if isinstance(part, str):
-        node = PythonNode(part, ast.parse(part, mode="eval"))
+        node = PythonNode(part.strip(), ast.parse(part.strip(), mode="eval"))
         return ReturnValueConcept(
             who="parsers.Default",
             status=True,
@@ -48,6 +50,16 @@ def get_concept_part(part):
                 parser=PythonParser(),
                 value=node))
 
+    if isinstance(part, PN):
+        node = PythonNode(part.source.strip(), ast.parse(part.source.strip(), mode=part.mode))
+        return ReturnValueConcept(
+            who="parsers.Default",
+            status=True,
+            value=ParserResultConcept(
+                source=part.source,
+                parser=PythonParser(),
+                value=node))
+
     if isinstance(part, PythonNode):
         return ReturnValueConcept(
             who="parsers.Default",
@@ -61,6 +73,12 @@ def get_concept_part(part):
         return part
 
 
+@dataclass
+class PN:
+    source: str  # parser result source
+    mode: str  # compilation mode
+
+
 class TestDefaultParser(TestUsingMemoryBasedSheerka):
 
     def init_parser(self, *concepts):
@@ -82,7 +100,7 @@ class TestDefaultParser(TestUsingMemoryBasedSheerka):
     ])
     def test_i_can_parse_def_concept(self, text, expected):
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         node = res.value.value
 
         assert res.status
@@ -99,14 +117,14 @@ post isinstance(res, int)
 as res = a + b
     """
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         return_value = res.value
         expected_concept = get_def_concept(
             name="a plus b",
-            where="a,b",
-            pre="isinstance(a, int) and isinstance(b, float)",
-            post="isinstance(res, int)",
-            body=PythonNode("res = a + b", ast.parse("res = a + b", mode="exec"))
+            where="a,b\n",
+            pre="isinstance(a, int) and isinstance(b, float)\n",
+            post="isinstance(res, int)\n",
+            body=PN("res = a + b\n    ", "exec")
         )
 
         assert res.status
@@ -119,17 +137,15 @@ def concept add one to a as
 def func(x):
     return x+1
 func(a)
-        """
+"""
 
         expected_concept = get_def_concept(
             name="add one to a ",
-            body=PythonNode(
-                "def func(x):\n    return x+1\nfunc(a)",
-                ast.parse("def func(x):\n    return x+1\nfunc(a)", mode="exec"))
+            body=PN("def func(x):\n    return x+1\nfunc(a)\n", "exec")
         )
 
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         return_value = res.value
 
         assert res.status
@@ -141,8 +157,7 @@ func(a)
 def concept add one to a as:
     def func(x):
         return x+1
-    func(a)
-    """
+    func(a)"""
 
         expected_concept = get_def_concept(
             name="add one to a ",
@@ -152,7 +167,7 @@ def concept add one to a as:
         )
 
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         return_value = res.value
 
         assert res.status
@@ -168,7 +183,7 @@ func(a)
     """
 
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         return_value = res.value
 
         assert not res.status
@@ -184,7 +199,7 @@ def concept add one to a as
     func(a)
         """
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         return_value = res.value
 
         assert not res.status
@@ -194,7 +209,7 @@ def concept add one to a as
         text = "def concept as 'hello'"
 
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         return_value = res.value
 
         assert not res.status
@@ -205,9 +220,9 @@ def concept add one to a as
     def test_concept_keyword_is_mandatory_but_the_concept_is_recognized(self):
         text = "def hello as a where b pre c post d"
 
-        expected_concept = get_def_concept(name="hello", body="a", where="b", pre="c", post="d")
+        expected_concept = get_def_concept(name="hello", body="a ", where="b ", pre="c ", post="d")
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         return_value = res.value
 
         assert not res.status
@@ -225,7 +240,7 @@ def concept add one to a as
     ])
     def test_i_can_detect_error_in_declaration(self, text):
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         return_value = res.value
 
         assert not res.status
@@ -235,7 +250,7 @@ def concept add one to a as
         text = "def concept hello \n my friend as 'hello'"
 
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         return_value = res.value
 
         assert not res.status
@@ -244,7 +259,7 @@ def concept add one to a as
     def test_i_can_parse_def_concept_from_bnf(self):
         text = "def concept name from bnf a_concept | 'a_string' as __definition[0]"
         sheerka, context, parser, a_concept = self.init_parser("a_concept")
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
 
         node = res.value.value
         definition = OrderedChoice(ConceptExpression(a_concept, rule_name="a_concept"), StrMatch("a_string"))
@@ -260,7 +275,7 @@ def concept add one to a as
     def test_i_can_parse_def_concept_where_bnf_references_itself(self):
         text = "def concept name from bnf 'a' + name?"
         sheerka, context, parser, a_concept = self.init_parser("a_concept")
-        parser.parse(context, text)
+        parser.parse(context, ParserInput(text))
 
         assert not parser.has_error
 
@@ -271,7 +286,7 @@ def concept add one to a as
     ])
     def test_i_can_detect_empty_bnf_declaration(self, text):
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
 
         assert not res.status
         assert res.value.value[0] == SyntaxErrorNode([], "Empty declaration")
@@ -281,7 +296,7 @@ def concept add one to a as
         "def concept addition from def a plus b as a + b"])
     def test_i_can_def_concept_from_definition(self, text):
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         expected = get_def_concept("addition", definition="a plus b", body="a + b")
         node = res.value.value
 
@@ -294,7 +309,7 @@ def concept add one to a as
     def test_i_can_detect_not_for_me(self):
         text = "hello world"
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
 
         assert not res.status
         assert context.sheerka.isinstance(res.value, BuiltinConcepts.NOT_FOR_ME)
@@ -303,7 +318,7 @@ def concept add one to a as
     def test_i_can_parse_is_a(self):
         text = "the name of my 'concept' isa the name of the set"
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         expected = IsaConceptNode([],
                                   concept=NameNode(list(Tokenizer("the name of my 'concept'"))),
                                   set=NameNode(list(Tokenizer("the name of the set"))))
@@ -323,7 +338,7 @@ def concept add one to a as
     ])
     def test_i_cannot_parse_invalid_entries(self, text):
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
 
         assert not res.status
         assert isinstance(res.body, ParserResultConcept)
@@ -339,10 +354,10 @@ def concept add one to a as
     ])
     def test_i_cannot_parse_when_tokenizer_fails(self, text, error_msg, error_text):
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
 
         assert not res.status
-        assert isinstance(res.body, ParserResultConcept)
+        assert sheerka.isinstance(res.body, BuiltinConcepts.ERROR)
         assert isinstance(res.body.body[0], LexerError)
         assert res.body.body[0].message == error_msg
         assert res.body.body[0].text == error_text
@@ -350,7 +365,7 @@ def concept add one to a as
     def test_i_cannot_parse_bnf_definition_referencing_unknown_concept(self):
         text = "def concept name from bnf unknown"
         sheerka, context, parser = self.init_parser()
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
 
         assert not res.status
         assert context.sheerka.isinstance(res.value, BuiltinConcepts.UNKNOWN_CONCEPT)
diff --git a/tests/parsers/test_ExactConceptParser.py b/tests/parsers/test_ExactConceptParser.py
index e3a0cdf..d4f1b82 100644
--- a/tests/parsers/test_ExactConceptParser.py
+++ b/tests/parsers/test_ExactConceptParser.py
@@ -1,5 +1,6 @@
 from core.builtin_concepts import BuiltinConcepts
 from core.concept import Concept, CMV
+from core.sheerka.services.SheerkaExecute import ParserInput
 from core.tokenizer import Tokenizer
 from parsers.ExactConceptParser import ExactConceptParser
 
@@ -55,7 +56,7 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
         concept = self.create_and_add_in_cache_concept(sheerka, "hello world")
 
         source = "hello world"
-        results = ExactConceptParser().parse(context, source)
+        results = ExactConceptParser().parse(context, ParserInput(source))
         concept_found = results[0].value.value
 
         assert len(results) == 1
@@ -71,7 +72,7 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
         self.create_and_add_in_cache_concept(sheerka, "hello a", variables=["a"])
 
         source = "hello world"
-        results = ExactConceptParser().parse(context, source)
+        results = ExactConceptParser().parse(context, ParserInput(source))
 
         assert len(results) == 2
         results = sorted(results, key=lambda x: x.value.value.name)  # because of the usage of sets
@@ -91,7 +92,7 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
         concept = self.create_and_add_in_cache_concept(sheerka, "a + b", ["a", "b"])
 
         source = "10 + 5"
-        results = ExactConceptParser().parse(context, source)
+        results = ExactConceptParser().parse(context, ParserInput(source))
 
         assert len(results) == 1
         assert results[0].status
@@ -107,7 +108,7 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
         concept = self.create_and_add_in_cache_concept(sheerka, "a + b + a", ["a", "b"])
 
         source = "10 + 5 + 10"
-        results = ExactConceptParser(max_word_size=5).parse(context, source)
+        results = ExactConceptParser(max_word_size=5).parse(context, ParserInput(source))
 
         assert len(results) == 1
         assert results[0].status
@@ -122,7 +123,7 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
         )
 
         source = "10 + 5"
-        results = ExactConceptParser().parse(context, source)
+        results = ExactConceptParser().parse(context, ParserInput(source))
         concept_found = results[0].value.value
 
         assert len(results) == 1
@@ -135,7 +136,7 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
         sheerka, context, foo = self.init_concepts("foo")
 
         source = "c:foo:"
-        results = ExactConceptParser().parse(context, source)
+        results = ExactConceptParser().parse(context, ParserInput(source))
         concept_found = results[0].value.value
 
         assert len(results) == 1
@@ -152,7 +153,7 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
         )
 
         source = "c:one: plus c:two:"
-        results = ExactConceptParser().parse(context, source)
+        results = ExactConceptParser().parse(context, ParserInput(source))
         concept_found = results[0].value.value
 
         assert len(results) == 1
@@ -168,7 +169,7 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
         )
 
         source = "z is a concept"
-        results = ExactConceptParser().parse(context, source)
+        results = ExactConceptParser().parse(context, ParserInput(source))
         concept_found = results[0].value.value
 
         assert len(results) == 1
@@ -178,7 +179,7 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
         assert not concept_found.metadata.is_evaluated
 
         source = "def concept z"
-        results = ExactConceptParser().parse(context, source)
+        results = ExactConceptParser().parse(context, ParserInput(source))
         concept_found = results[0].value.value
 
         assert len(results) == 1
@@ -190,7 +191,7 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
     def test_i_can_manage_unknown_concept(self):
         context = self.get_context(self.get_sheerka(singleton=True))
         source = "def concept hello"  # this is not a concept by itself
-        res = ExactConceptParser().parse(context, source)
+        res = ExactConceptParser().parse(context, ParserInput(source))
 
         assert not res.status
         assert context.sheerka.isinstance(res.value, BuiltinConcepts.UNKNOWN_CONCEPT)
@@ -199,7 +200,7 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
     def test_i_can_detect_concepts_too_long(self):
         context = self.get_context(self.get_sheerka(singleton=True))
         source = "a very but finally too long concept"
-        res = ExactConceptParser().parse(context, source)
+        res = ExactConceptParser().parse(context, ParserInput(source))
 
         assert not res.status
         assert context.sheerka.isinstance(res.value, BuiltinConcepts.NOT_FOR_ME)
@@ -207,15 +208,15 @@ class TestExactConceptParser(TestUsingMemoryBasedSheerka):
         assert res.value.reason.body == source
         assert res.value.body == source
 
-    def test_i_can_detect_concept_from_tokens(self):
-        context = self.get_context(self.get_sheerka(singleton=True))
-        concept = get_concept("hello world", [])
-        context.sheerka.add_in_cache(concept)
-
-        source = "hello world"
-        results = ExactConceptParser().parse(context, list(Tokenizer(source)))
-
-        assert len(results) == 1
-        assert results[0].status
-        assert results[0].value.value == concept
-        assert not results[0].value.value.metadata.need_validation
+    # def test_i_can_detect_concept_from_tokens(self):
+    #     context = self.get_context(self.get_sheerka(singleton=True))
+    #     concept = get_concept("hello world", [])
+    #     context.sheerka.add_in_cache(concept)
+    #
+    #     source = "hello world"
+    #     results = ExactConceptParser().parse(context, list(Tokenizer(source)))
+    #
+    #     assert len(results) == 1
+    #     assert results[0].status
+    #     assert results[0].value.value == concept
+    #     assert not results[0].value.value.metadata.need_validation
diff --git a/tests/parsers/test_PythonParser.py b/tests/parsers/test_PythonParser.py
index 6afaa5a..ba17227 100644
--- a/tests/parsers/test_PythonParser.py
+++ b/tests/parsers/test_PythonParser.py
@@ -3,7 +3,8 @@ import ast
 import core.utils
 import pytest
 from core.builtin_concepts import ParserResultConcept, NotForMeConcept
-from core.tokenizer import Tokenizer, LexerError
+from core.sheerka.services.SheerkaExecute import ParserInput
+from core.tokenizer import LexerError
 from parsers.PythonParser import PythonNode, PythonParser, PythonErrorNode
 
 from tests.TestUsingMemoryBasedSheerka import TestUsingMemoryBasedSheerka
@@ -17,21 +18,7 @@ class TestPythonParser(TestUsingMemoryBasedSheerka):
     ])
     def test_i_can_parse_a_simple_expression(self, text, expected):
         parser = PythonParser()
-        res = parser.parse(self.get_context(), text)
-
-        assert res.status
-        assert res.who == parser.name
-        assert isinstance(res.value, ParserResultConcept)
-        assert res.value.value == expected
-
-    @pytest.mark.parametrize("text, expected", [
-        ("1+1", PythonNode("1+1", ast.parse("1+1", mode="eval"))),
-        ("a=10", PythonNode("a=10", ast.parse("a=10", mode="exec"))),
-    ])
-    def test_i_can_parse_from_tokens(self, text, expected):
-        parser = PythonParser()
-        tokens = list(Tokenizer(text))
-        res = parser.parse(self.get_context(), tokens)
+        res = parser.parse(self.get_context(), ParserInput(text))
 
         assert res.status
         assert res.who == parser.name
@@ -40,12 +27,11 @@ class TestPythonParser(TestUsingMemoryBasedSheerka):
 
     @pytest.mark.parametrize("text", [
         "1+",
-        "'name",
-        "foo = 'name"
+        "&#é",
     ])
-    def test_i_can_detect_error(self, text):
+    def test_i_can_detect_python_error(self, text):
         parser = PythonParser()
-        res = parser.parse(self.get_context(), text)
+        res = parser.parse(self.get_context(), ParserInput(text))
 
         assert not res.status
         assert res.who == parser.name
@@ -61,7 +47,7 @@ class TestPythonParser(TestUsingMemoryBasedSheerka):
     ])
     def test_i_can_detect_lexer_errors(self, text, error_msg, error_text):
         parser = PythonParser()
-        res = parser.parse(self.get_context(), text)
+        res = parser.parse(self.get_context(), ParserInput(text))
 
         assert not res.status
         assert isinstance(res.value, NotForMeConcept)
@@ -76,12 +62,13 @@ class TestPythonParser(TestUsingMemoryBasedSheerka):
         text = "c:name|id: + 1"
 
         parser = PythonParser()
-        res = parser.parse(self.get_context(), text)
+        res = parser.parse(self.get_context(), ParserInput(text))
         encoded = core.utils.encode_concept(("name", "id"))
 
         assert res
+        assert res.value.source == "c:name|id: + 1"
         assert res.value.value == PythonNode(
-            "c:name|id: + 1",
+            "__C__KEY_name__ID_id__C__ + 1",
             ast.parse(encoded + "+1", mode="eval"))
         assert res.value.value.concepts == {
             encoded: ("name", "id")
diff --git a/tests/parsers/test_PythonWithConceptsParser.py b/tests/parsers/test_PythonWithConceptsParser.py
index dfcb899..8ea43bf 100644
--- a/tests/parsers/test_PythonWithConceptsParser.py
+++ b/tests/parsers/test_PythonWithConceptsParser.py
@@ -3,6 +3,7 @@ import ast
 import pytest
 from core.builtin_concepts import ParserResultConcept, BuiltinConcepts, ReturnValueConcept
 from core.concept import Concept
+from core.sheerka.services.SheerkaExecute import ParserInput
 from core.tokenizer import Token, TokenKind, Tokenizer
 from parsers.BaseNodeParser import ConceptNode, UnrecognizedTokensNode
 from parsers.PythonParser import PythonNode
@@ -38,6 +39,7 @@ class TestPythonWithConceptsParser(TestUsingMemoryBasedSheerka):
 
     @pytest.mark.parametrize("text, interested", [
         ("not parser result", False),
+        (ParserInput("not parser result"), False),
         (ParserResultConcept(parser="not multiple_concepts_parser"), False),
         (ParserResultConcept(parser=unrecognized_nodes_parser, value=[UnrecognizedTokensNode(0, 0, [])]), True),
     ])
diff --git a/tests/parsers/test_SyaNodeParser.py b/tests/parsers/test_SyaNodeParser.py
index ff6b060..dcd8541 100644
--- a/tests/parsers/test_SyaNodeParser.py
+++ b/tests/parsers/test_SyaNodeParser.py
@@ -2,6 +2,7 @@ import pytest
 from core.builtin_concepts import BuiltinConcepts
 from core.concept import Concept, CC
 from core.sheerka.services.SheerkaComparisonManager import SheerkaComparisonManager
+from core.sheerka.services.SheerkaExecute import ParserInput
 from core.tokenizer import Tokenizer
 from parsers.BaseNodeParser import utnode, ConceptNode, cnode, short_cnode, UnrecognizedTokensNode, \
     SCWC, CNC, UTN
@@ -198,7 +199,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_can_post_fix_simple_infix_concepts(self, expression, expected_sequences):
         sheerka, context, parser = self.init_parser()
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         assert len(res) == len(expected_sequences)
         for res_i, expected in zip(res, expected_sequences):
@@ -224,7 +225,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         }
         sheerka, context, parser = self.init_parser(concepts_map, create_new=True, init_from_sheerka=True)
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         assert len(res) == len(expected_sequences)
         for res_i, expected in zip(res, expected_sequences):
@@ -248,7 +249,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_can_post_fix_simple_prefixed_concepts(self, expression, expected_sequences):
         sheerka, context, parser = self.init_parser()
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         assert len(res) == len(expected_sequences)
         for res_i, expected in zip(res, expected_sequences):
@@ -291,7 +292,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         }
         sheerka, context, parser = self.init_parser(concepts_map, create_new=True, init_from_sheerka=True)
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         assert len(res) == len(expected_sequences)
         for res_i, expected in zip(res, expected_sequences):
@@ -315,7 +316,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_can_post_fix_simple_suffixed_concepts(self, expression, expected_sequences):
         sheerka, context, parser = self.init_parser()
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         assert len(res) == len(expected_sequences)
         for res_i, expected in zip(res, expected_sequences):
@@ -337,7 +338,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         }
         sheerka, context, parser = self.init_parser(concepts_map, None)
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = compute_expected_array(concepts_map, expression, expected)
         assert len(res) == 1
         assert res[0].out == expected_array
@@ -377,7 +378,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
 
         sheerka, context, parser = self.init_parser()
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         assert len(res) == len(expected_sequences)
         for res_i, expected in zip(res, expected_sequences):
@@ -409,7 +410,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         }
         sheerka, context, parser = self.init_parser(concepts_map, create_new=True, init_from_sheerka=True)
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         assert len(res) == len(expected_sequences)
         for res_i, expected in zip(res, expected_sequences):
@@ -430,7 +431,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         }
         sheerka, context, parser = self.init_parser(concepts_map, None)
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = compute_expected_array(concepts_map, expression, expected)
 
         assert len(res) == 1
@@ -453,7 +454,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         }
         sheerka, context, parser = self.init_parser(concepts_map, sya_def)
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = compute_expected_array(concepts_map, expression, expected)
 
         assert len(res) == 1
@@ -468,7 +469,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_can_post_fix_binary_with_precedence(self, expression, expected):
         sheerka, context, parser = self.init_parser()
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = compute_expected_array(cmap, expression, expected)
 
         assert len(res) == 1
@@ -489,7 +490,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
 
         expression = "suffixed a prefixed"
         expected = ["a", "prefixed", "suffixed"]
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = compute_expected_array(concepts_map, expression, expected)
 
         assert len(res) == 1
@@ -504,7 +505,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
 
         expression = "suffixed a prefixed"
         expected = ["a", "suffixed", "prefixed"]
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = compute_expected_array(concepts_map, expression, expected)
 
         assert len(res) == 1
@@ -524,7 +525,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser(concepts_map, sya_def)
 
         expression = "one equals two equals three"
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         expected = ["one", "two", "three", ("equals", 1), "equals"]
         expected_array = compute_expected_array(concepts_map, expression, expected)
@@ -546,7 +547,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser(concepts_map, sya_def)
 
         expression = "one plus two plus three"
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         expected = ["one", "two", "plus", "three", ("plus", 1)]
         expected_array = compute_expected_array(concepts_map, expression, expected)
@@ -576,7 +577,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         }
         sheerka, context, parser = self.init_parser(concepts_map, sya_def)
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = compute_expected_array(concepts_map, expression, expected)
         assert len(res) == 1
         assert res[0].out == expected_array
@@ -603,7 +604,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         }
         sheerka, context, parser = self.init_parser(concepts_map, sya_def)
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = compute_expected_array(concepts_map, expression, expected)
         assert len(res) == 1
         assert res[0].out == expected_array
@@ -617,7 +618,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser(concepts_map, None)
 
         expression = "foo bar baz"
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_sequences = [
             [UTN("bar "), "foo", "baz"],
             ["baz", "foo bar"]
@@ -664,7 +665,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_can_pos_fix_when_parenthesis(self, expression, expected):
         sheerka, context, parser = self.init_parser()
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = compute_expected_array(cmap, expression, expected)
 
         assert len(res) == 1
@@ -719,7 +720,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_can_post_fix_when_parenthesis_and_unknown(self, expression, expected_sequences):
         sheerka, context, parser = self.init_parser()
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         assert len(res) == len(expected_sequences)
         for res_i, expected in zip(res, expected_sequences):
@@ -745,7 +746,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_can_detect_parenthesis_mismatch_error_when_post_fixing(self, expression, expected):
         sheerka, context, parser = self.init_parser()
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         assert len(res) == 1
         assert res[0].errors == [expected]
@@ -756,7 +757,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_can_detected_when_too_many_parameters(self, expression, expected):
         sheerka, context, parser = self.init_parser(cmap, None)
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         assert len(res) == 1
         assert len(res[0].errors) == 1
@@ -790,7 +791,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_can_post_fix_sequences(self, expression, expected):
         sheerka, context, parser = self.init_parser()
 
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = compute_expected_array(cmap, expression, expected)
 
         assert len(res) == 1
@@ -808,7 +809,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser()
 
         expected = ["one", "two", "three", "?"]
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = compute_expected_array(cmap, expression, expected)
 
         assert len(res) == 1
@@ -830,7 +831,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser(concepts_map, sya_def)
 
         expression = "a plus plus equals b"
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
         expected_array = tests.parsers.parsers_utils.compute_debug_array(res)
         assert expected_array == [
             ["T(a)", "C(a plus b)", "C(a plus b)", "T(equals)", "T(b)"],
@@ -859,9 +860,9 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser(concepts_map, sya_def)
 
         expression = "a plus complex infix b"
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
-        res = parser.parse(context, expression)
+        res = parser.parse(context, ParserInput(expression))
         pass
 
     def test_i_can_use_string_instead_of_identifier(self):
@@ -874,7 +875,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
 
         sheerka, context, parser = self.init_parser(concepts_map, None)
 
-        res = parser.infix_to_postfix(context, "one ? ? two '::' three")
+        res = parser.infix_to_postfix(context, ParserInput("one ? ? two '::' three"))
         assert len(res) == 1
         assert res[0].out == [
             cnode("one", start=0, end=0, source="one"),
@@ -896,7 +897,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
 
         sheerka, context, parser = self.init_parser(concepts_map, sya_def)
 
-        res = parser.infix_to_postfix(context, "one less than two less than three")
+        res = parser.infix_to_postfix(context, ParserInput("one less than two less than three"))
         assert len(res) == 1
         assert res[0].errors == [NoneAssociativeSequenceErrorNode(concepts_map["less than"], 2, 8)]
 
@@ -909,7 +910,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser()
 
         expression = "suffixed twenties"
-        res = parser.infix_to_postfix(context, expression)
+        res = parser.infix_to_postfix(context, ParserInput(expression))
 
         expected = [cnode("twenties", 2, 2, "twenties"), "suffixed"]
         expected_array = compute_expected_array(cmap, expression, expected)
@@ -920,7 +921,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser()
 
         text = "one plus two mult three"
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         wrapper = res.body
         lexer_nodes = res.body.body
 
@@ -939,7 +940,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser()
 
         text = "suffixed 1 + 1"
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         wrapper = res.body
         lexer_nodes = res.body.body
 
@@ -962,7 +963,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser()
 
         text = "suffixed twenty one"
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         assert len(res) == 2
         assert res[1].status
 
@@ -981,7 +982,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         sheerka, context, parser = self.init_parser()
 
         text = "one plus 1 + 1 suffixed two"
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         wrapper = res.body
         lexer_nodes = res.body.body
 
@@ -1020,7 +1021,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_can_parse_when_one_result(self, text, expected_status, expected_result):
         sheerka, context, parser = self.init_parser()
 
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         wrapper = res.body
         lexer_nodes = res.body.body
 
@@ -1043,7 +1044,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         """
         sheerka, context, parser = self.init_parser()
 
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
 
         assert not res.status
         assert sheerka.isinstance(res.body, BuiltinConcepts.NOT_FOR_ME)
@@ -1068,7 +1069,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         """
         sheerka, context, parser = self.init_parser()
 
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
 
         wrapper = res.body
         lexer_nodes = res.body.body
@@ -1088,7 +1089,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_cannot_parse_when_unrecognized(self, text, expected_concept, expected_unrecognized):
         sheerka, context, parser = self.init_parser()
 
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         wrapper = res.body
         lexer_nodes = res.body.body
         expected_end = len(list(Tokenizer(text))) - 2
@@ -1108,7 +1109,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_cannot_parse_when_part_of_the_sequence_is_not_recognized(self, text, expected):
         sheerka, context, parser = self.init_parser()
 
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
         wrapper = res.body
         lexer_nodes = res.body.body
 
@@ -1132,7 +1133,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
         """
         sheerka, context, parser = self.init_parser()
 
-        res = parser.parse(context, text)
+        res = parser.parse(context, ParserInput(text))
 
         assert not res.status
         assert sheerka.isinstance(res.body, BuiltinConcepts.NOT_FOR_ME)
@@ -1141,7 +1142,7 @@ class TestSyaNodeParser(TestUsingMemoryBasedSheerka):
     def test_i_cannot_parse_empty_string(self):
         sheerka, context, parser = self.init_parser({}, None)
 
-        res = parser.parse(context, "")
+        res = parser.parse(context, ParserInput(""))
 
         assert not res.status
         assert sheerka.isinstance(res.body, BuiltinConcepts.IS_EMPTY)
diff --git a/tests/parsers/test_UnrecognizedNodeParser.py b/tests/parsers/test_UnrecognizedNodeParser.py
index 22fe8e3..0f0e8b4 100644
--- a/tests/parsers/test_UnrecognizedNodeParser.py
+++ b/tests/parsers/test_UnrecognizedNodeParser.py
@@ -135,7 +135,7 @@ class TestUnrecognizedNodeParser(TestUsingMemoryBasedSheerka):
         assert sheerka.isinstance(concept.compiled["d"][0], BuiltinConcepts.RETURN_VALUE)
         assert concept.compiled["d"][0].status
         assert concept.compiled["d"][0].who == "parsers.Python"
-        assert concept.compiled["d"][0].body.source == "1 + 2"
+        assert concept.compiled["d"][0].body.source == " 1 + 2 "
 
         assert len(concept.compiled["e"]) == 1
         assert sheerka.isinstance(concept.compiled["e"][0], BuiltinConcepts.RETURN_VALUE)
@@ -171,13 +171,13 @@ class TestUnrecognizedNodeParser(TestUsingMemoryBasedSheerka):
         assert len(res.body.concept.compiled["a"]) == 1
         assert res.body.concept.compiled["a"][0].status
         assert res.body.concept.compiled["a"][0].who == "parsers.Python"
-        assert res.body.concept.compiled["a"][0].body.source == "1"
+        assert res.body.concept.compiled["a"][0].body.source == "1 "
 
         assert res.body.concept.compiled["b"] == concepts_map["mult"]
         assert sheerka.isinstance(res.body.concept.compiled["b"].compiled["a"][0], BuiltinConcepts.RETURN_VALUE)
         assert res.body.concept.compiled["b"].compiled["a"][0].status
         assert res.body.concept.compiled["b"].compiled["a"][0].who == "parsers.Python"
-        assert res.body.concept.compiled["b"].compiled["a"][0].body.source == "2"
+        assert res.body.concept.compiled["b"].compiled["a"][0].body.source == " 2 "
 
         assert sheerka.isinstance(res.body.concept.compiled["b"].compiled["b"][0], BuiltinConcepts.RETURN_VALUE)
         assert res.body.concept.compiled["b"].compiled["b"][0].status