Implemented a first and basic version of a Rete rule engine

src/core/tokenizer.py

@@ -139,6 +139,7 @@ class LexerError(Exception):
 class Keywords(Enum):
     DEF = "def"
     CONCEPT = "concept"
+    RULE = "rule"
     FROM = "from"
     BNF = "bnf"
     AS = "as"
@@ -149,6 +150,7 @@ class Keywords(Enum):
     RET = "ret"
     WHEN = "when"
     PRINT = "print"
+    THEN = "then"
 
 
 class Tokenizer:
@@ -557,36 +559,3 @@ class IterParser:
             return token_after
         except StopIteration:
             return Token(TokenKind.EOF, -1, -1, -1, -1)
-
-
-# @dataclass
-# class PropDef:
-#     prop: str
-#     index: int
-#
-#
-# class SimpleExpressionParser(IterParser):
-#     def __init__(self, source):
-#         super().__init__(source)
-#         self.properties = []
-#
-#     def parse(self):
-#
-#         prop, index, key = None, None, None
-#         while self.next_token():
-#             if self.token.type == TokenKind.DOT:
-#                 self.properties.append(PropDef(prop, index, key))
-#                 prop, index, key = None, None, None
-#                 continue
-#
-#             if self.token.type == TokenKind.LBRACKET:
-#                 index = self.parse_index()
-#             elif self.token.type == TokenKind.LBRACE:
-#                 key = self.parse_key()
-#             else:
-#                 prop = self.token.value
-#
-#         if prop is not None:
-#             self.properties.append(PropDef(prop, index, key))
-#
-#     def parse_i