diff --git a/core/concept.py b/core/concept.py
index 3af285e..7f01891 100644
--- a/core/concept.py
+++ b/core/concept.py
@@ -12,8 +12,7 @@ class Concept:
         self.is_builtin = is_builtin
         self.pre = None  # list of pre conditions before calling the main function
         self.post = None  # list of post conditions after calling the main function
-        self.main = None   # main method
-        self.value = None  # value of the concept
+        self.main = None   # main method, can also be the value of the concept
         self.id = Concept.concepts_id
         Concept.concepts_id = Concept.concepts_id + 1
 
diff --git a/docs/syntax.md b/docs/syntax_v1.md
similarity index 100%
rename from docs/syntax.md
rename to docs/syntax_v1.md
diff --git a/docs/syntax_v2.md b/docs/syntax_v2.md
new file mode 100644
index 0000000..9cfeec6
--- /dev/null
+++ b/docs/syntax_v2.md
@@ -0,0 +1,20 @@
+```
+def concept one as 1  --> creates a new concept 1
+def concept two as 2  --> creates a new concept 2
+def concept add(a,b) as a + b   --> create concept that need parenthesis
+def concept a plus b as add(a,b)  --> create a concept that mimic human language
+
+one plus two --> recognizes the concept 'a plus b'
+one plus two ? --> makes the addition
+
+concept a plus b --> will work on this concept
+pre: a is a number 
+
+--> ERROR : 'a is a number' is not known
+
+def concept a is a number as :
+    isinstanceof(a, number) 
+
+--> adds concept a is a number
+--> add the pre condition to the concept a plus b
+```
\ No newline at end of file
diff --git a/main.py b/main.py
index 0cfd4e6..18322cf 100644
--- a/main.py
+++ b/main.py
@@ -15,7 +15,7 @@ def main():
     # launch the parsers
 
     # execute the concepts
-
+    print(event_as_string)
     return True
 
 
diff --git a/p.txt b/p.txt
new file mode 100644
index 0000000..11b15b1
--- /dev/null
+++ b/p.txt
@@ -0,0 +1 @@
+print("hello")
diff --git a/parsers/__init__.py b/parsers/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/parsers/defaultparser.py b/parsers/defaultparser.py
new file mode 100644
index 0000000..b0d4a2e
--- /dev/null
+++ b/parsers/defaultparser.py
@@ -0,0 +1,249 @@
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class Token:
+    type: str
+    value: str
+    index: int
+    line: int
+    column: int
+
+
+@dataclass(frozen=True)
+class LexerError(Exception):
+    message: str
+    text: str
+    index: int
+    line: int
+    column: int
+
+
+class Tokens:
+    EOF = "eof"
+    WHITESPACE = "whitespace"
+    NEWLINE = "newline"
+    KEYWORD = "keyword"
+    IDENTIFIER = "identifier"
+    STRING = "string"
+    NUMBER = "number"
+    TRUE = "true"
+    FALSE = "false"
+    LPAR = "lpar"
+    RPAR = "rpar"
+    LBRACKET = "lbrace"
+    RBRACKET = "rbracket"
+    LBRACE = "lbrace"
+    RBRACE = "rbrace"
+    PLUS = "plus"
+    MINUS = "minus"
+    STAR = "star"
+    SLASH = "slash"
+    PERCENT = "percent"
+    COMMA = "comma"
+    SEMICOLON = "semicolon"
+    COLON = "colon"
+    DOT = "dot"
+    QMARK = "qmark"
+    VBAR = "vbar"
+    AMPER = "amper"
+
+
+class TokenIter:
+    KEYWORDS = ("def", "concept", "as", "pre", "post")
+
+    """
+    Class that can iterate on the tokens
+    """
+
+    def __init__(self, text):
+        self.text = text
+        self.text_len = len(text)
+
+    def __iter__(self):
+
+        i = 0
+        line = 1
+        column = 1
+        while i < self.text_len:
+            c = self.text[i]
+            if c == "+":
+                yield Token(Tokens.PLUS, "+", i, line, column)
+                i += 1
+                column += 1
+            elif c == "-":
+                if i + 1 < self.text_len and self.text[i + 1].isdigit():
+                    number = self.eat_number(i)
+                    yield Token(Tokens.NUMBER, number, i, line, column)
+                    i += len(number)
+                    column += len(number)
+                else:
+                    yield Token(Tokens.MINUS, "-", i, line, column)
+                    i += 1
+                    column += 1
+            elif c == "/":
+                yield Token(Tokens.SLASH, "/", i, line, column)
+                i += 1
+                column += 1
+            elif c == "*":
+                yield Token(Tokens.STAR, "*", i, line, column)
+                i += 1
+                column += 1
+            elif c == "{":
+                yield Token(Tokens.LBRACE, "{", i, line, column)
+                i += 1
+                column += 1
+            elif c == "}":
+                yield Token(Tokens.RBRACE, "}", i, line, column)
+                i += 1
+                column += 1
+            elif c == "(":
+                yield Token(Tokens.LPAR, "(", i, line, column)
+                i += 1
+                column += 1
+            elif c == ")":
+                yield Token(Tokens.RPAR, ")", i, line, column)
+                i += 1
+                column += 1
+            elif c == "[":
+                yield Token(Tokens.LBRACKET, "[", i, line, column)
+                i += 1
+                column += 1
+            elif c == "]":
+                yield Token(Tokens.RBRACKET, "]", i, line, column)
+                i += 1
+                column += 1
+            elif c == " " or c == "\t":
+                whitespace = self.eat_whitespace(i)
+                yield Token(Tokens.WHITESPACE, whitespace, i, line, column)
+                i += len(whitespace)
+                column += len(whitespace)
+            elif c == ",":
+                yield Token(Tokens.COMMA, ",", i, line, column)
+                i += 1
+                column += 1
+            elif c == ".":
+                yield Token(Tokens.DOT, ".", i, line, column)
+                i += 1
+                column += 1
+            elif c == ";":
+                yield Token(Tokens.SEMICOLON, ";", i, line, column)
+                i += 1
+                column += 1
+            elif c == ":":
+                yield Token(Tokens.COLON, ":", i, line, column)
+                i += 1
+                column += 1
+            elif c == "?":
+                yield Token(Tokens.QMARK, "?", i, line, column)
+                i += 1
+                column += 1
+            elif c == "\n" or c == "\r":
+                newline = self.eat_newline(i)
+                yield Token(Tokens.NEWLINE, newline, i, line, column)
+                i += len(newline)
+                column = 1
+                line += 1
+            elif c.isalpha() or c == "_":
+                identifier = self.eat_identifier(i)
+                type = Tokens.KEYWORD if identifier in self.KEYWORDS else Tokens.IDENTIFIER
+                yield Token(type, identifier, i, line, column)
+                i += len(identifier)
+                column += len(identifier)
+            elif c.isdigit():
+                number = self.eat_number(i)
+                yield Token(Tokens.NUMBER, number, i, line, column)
+                i += len(number)
+                column += len(number)
+            elif c == "'" or c == '"':
+                string, newlines = self.eat_string(i)
+                yield Token(Tokens.STRING, string, i, line, column)
+                i += len(string)
+                column = 1 if newlines > 0 else column + len(string)
+                line += newlines
+            else:
+                raise LexerError(f"Unknown token '{c}'", self.text, i, line, column)
+
+        yield Token(Tokens.EOF, "", i, line, column)
+
+    def eat_whitespace(self, start):
+        result = self.text[start]
+        i = start + 1
+        while i < self.text_len:
+            c = self.text[i]
+            if c == " " or c == "\t":
+                result += c
+                i += 1
+            else:
+                break
+
+        return result
+
+    def eat_newline(self, start):
+        if start + 1 == self.text_len:
+            return self.text[start]
+
+        current = self.text[start]
+        next = self.text[start + 1]
+        if current == "\n" and next == "\r" or current == "\r" and next == "\n":
+            return current + next
+
+        return current
+
+    def eat_identifier(self, start):
+        result = self.text[start]
+        i = start + 1
+        while i < self.text_len:
+            c = self.text[i]
+            if c.isalpha() or c == "_" or c == "-" or c.isdigit():
+                result += c
+                i += 1
+            else:
+                break
+
+        return result
+
+    def eat_number(self, start):
+        result = self.text[start]
+        i = start + 1
+        while i < self.text_len:
+            c = self.text[i]
+            if c.isdigit() or c == ".":
+                result += c
+                i += 1
+            else:
+                break
+
+        return result
+
+    def eat_string(self, start):
+        quote = self.text[start]
+        result = self.text[start]
+        lines_count = 0
+
+        i = start + 1
+        escape = False
+        newline = None
+        while i < self.text_len:
+            c = self.text[i]
+            result += c
+            i += 1
+
+            if newline:
+                lines_count += 1
+                newline = c if c == newline else None
+            else:
+                if c == "\r" or c == "\n":
+                    newline = c
+
+            if c == "\\":
+                escape = True
+            elif c == quote and not escape:
+                break
+            else:
+                escape = False
+
+        if newline:
+            lines_count += 1
+
+        return result, lines_count
diff --git a/tests/test_defautparser.py b/tests/test_defautparser.py
new file mode 100644
index 0000000..ee43553
--- /dev/null
+++ b/tests/test_defautparser.py
@@ -0,0 +1,96 @@
+import pytest
+from parsers.defaultparser import TokenIter, Token, Tokens
+
+
+def test_i_can_tokenize():
+    source = "+*-/{}[]()    ,;:.?\n\n\r\r\r\nidentifier_0\t  \t10.15 10 'string\n' \"another string\""
+    tokens = list(TokenIter(source))
+    assert tokens[0] == Token(Tokens.PLUS, "+", 0, 1, 1)
+    assert tokens[1] == Token(Tokens.STAR, "*", 1, 1, 2)
+    assert tokens[2] == Token(Tokens.MINUS, "-", 2, 1, 3)
+    assert tokens[3] == Token(Tokens.SLASH, "/", 3, 1, 4)
+    assert tokens[4] == Token(Tokens.LBRACE, "{", 4, 1, 5)
+    assert tokens[5] == Token(Tokens.RBRACE, "}", 5, 1, 6)
+    assert tokens[6] == Token(Tokens.LBRACKET, "[", 6, 1, 7)
+    assert tokens[7] == Token(Tokens.RBRACKET, "]", 7, 1, 8)
+    assert tokens[8] == Token(Tokens.LPAR, "(", 8, 1, 9)
+    assert tokens[9] == Token(Tokens.RPAR, ")", 9, 1, 10)
+    assert tokens[10] == Token(Tokens.WHITESPACE, "    ", 10, 1, 11)
+    assert tokens[11] == Token(Tokens.COMMA, ",", 14, 1, 15)
+    assert tokens[12] == Token(Tokens.SEMICOLON, ";", 15, 1, 16)
+    assert tokens[13] == Token(Tokens.COLON, ":", 16, 1, 17)
+    assert tokens[14] == Token(Tokens.DOT, ".", 17, 1, 18)
+    assert tokens[15] == Token(Tokens.QMARK, "?", 18, 1, 19)
+    assert tokens[16] == Token(Tokens.NEWLINE, "\n", 19, 1, 20)
+    assert tokens[17] == Token(Tokens.NEWLINE, "\n\r", 20, 2, 1)
+    assert tokens[18] == Token(Tokens.NEWLINE, "\r", 22, 3, 1)
+    assert tokens[19] == Token(Tokens.NEWLINE, "\r\n", 23, 4, 1)
+    assert tokens[20] == Token(Tokens.IDENTIFIER, "identifier_0", 25, 5, 1)
+    assert tokens[21] == Token(Tokens.WHITESPACE, "\t  \t", 37, 5, 13)
+    assert tokens[22] == Token(Tokens.NUMBER, "10.15", 41, 5, 17)
+    assert tokens[23] == Token(Tokens.WHITESPACE, " ", 46, 5, 22)
+    assert tokens[24] == Token(Tokens.NUMBER, "10", 47, 5, 23)
+    assert tokens[25] == Token(Tokens.WHITESPACE, " ", 49, 5, 25)
+    assert tokens[26] == Token(Tokens.STRING, "'string\n'", 50, 5, 26)
+    assert tokens[27] == Token(Tokens.WHITESPACE, " ", 59, 6, 1)
+    assert tokens[28] == Token(Tokens.STRING, '"another string"', 60, 6, 2)
+
+
+@pytest.mark.parametrize("text, expected", [
+    ("_ident", True),
+    ("ident", True),
+    ("ident123", True),
+    ("ident_123", True),
+    ("ident-like-this", True),
+    ("àèùéû", True),
+    ("011254", False),
+    ("0abcd", False),
+    ("-abcd", False)
+])
+def test_i_can_tokenize_identifiers(text, expected):
+    tokens = list(TokenIter(text))
+    comparison = tokens[0].type == Tokens.IDENTIFIER
+    assert comparison == expected
+
+
+@pytest.mark.parametrize("text, expected_text, expected_newlines", [
+    ("'foo'", "'foo'", 0),
+    ('"foo"', '"foo"', 0),
+    ("'foo\rbar'", "'foo\rbar'", 1),
+    ("'foo\nbar'", "'foo\nbar'", 1),
+    ("'foo\n\rbar'", "'foo\n\rbar'", 1),
+    ("'foo\r\nbar'", "'foo\r\nbar'", 1),
+    ("'foo\r\rbar'", "'foo\r\rbar'", 2),
+    ("'foo\n\nbar'", "'foo\n\nbar'", 2),
+    ("'foo\r\n\n\rbar'", "'foo\r\n\n\rbar'", 2),
+    ("'\rfoo\rbar\r'", "'\rfoo\rbar\r'", 3),
+    ("'\nfoo\nbar\n'", "'\nfoo\nbar\n'", 3),
+    ("'\n\rfoo\r\n'", "'\n\rfoo\r\n'", 2),
+    (r"'foo\'bar'", r"'foo\'bar'", 0),
+    (r'"foo\"bar"', r'"foo\"bar"', 0),
+    ('"foo"bar"', '"foo"', 0),
+    ("'foo'bar'", "'foo'", 0),
+])
+def test_i_can_parse_strings(text, expected_text, expected_newlines):
+    lexer = TokenIter(text)
+    text_found, nb_of_newlines = lexer.eat_string(0)
+
+    assert nb_of_newlines == expected_newlines
+    assert text_found == expected_text
+
+
+@pytest.mark.parametrize("text", [
+    "1", "3.1415", "0.5", "01", "-5", "-5.10"
+])
+def test_i_can_parse_numbers(text):
+    tokens = list(TokenIter(text))
+    assert tokens[0].type == Tokens.NUMBER
+    assert tokens[0].value == text
+
+
+@pytest.mark.parametrize("text", [
+    "def", "concept", "as", "pre", "post"
+])
+def test_i_can_recognize_keywords(text):
+    tokens = list(TokenIter(text))
+    assert tokens[0].type == Tokens.KEYWORD