+ return (True, index, FurExpressionStatement(expression=expression))
+
+BUILTINS = {'print', 'pow'}
+
+def _assignment_statement_parser(index, tokens):
+ failure = (False, index, None)
+
+ if tokens[index].type == 'symbol':
+ target = tokens[index].match
+ target_assignment_line = tokens[index].line
+
+ index += 1
+ else:
+ return failure
+
+
+ if tokens[index].type == 'assignment_operator':
+ if target in BUILTINS:
+ raise Exception(
+ 'Trying to assign to builtin "{}" on line {}'.format(target, target_assignment_line),
+ )
+ assignment_operator_index = index
+ else:
+ return failure
+
+ success, index, expression = _expression_parser(index + 1, tokens)
+
+ if not success:
+ raise Exception(
+ 'Expected expression after assignment operator on line {}'.format(
+ tokens[assignment_operator_index].line
+ )
+ )
+
+ return True, index, FurAssignmentStatement(target=target, expression=expression)
+
+def _function_definition_statement_parser(index, tokens):
+ failure = (False, index, None)
+
+ if tokens[index].type == 'keyword' and tokens[index].match == 'def':
+ index += 1
+ else:
+ return failure
+
+ if tokens[index].type == 'symbol':
+ name = tokens[index].match
+ index += 1
+ else:
+ raise Exception('Expected function name, found "{}" on line {}'.format(
+ tokens[index].match,
+ tokens[index].line,
+ ))
+
+ if tokens[index].type == 'open_parenthese':
+ index += 1
+ else:
+ raise Exception('Expected "(", found "{}" on line {}'.format(
+ tokens[index].match,
+ tokens[index].line,
+ ))
+
+ success, index, argument_name_list = _comma_separated_list_parser(_symbol_expression_parser)(
+ index,
+ tokens,
+ )
+
+ if tokens[index].type == 'close_parenthese':
+ index += 1
+ else: