+ if tokens[index].type == 'colon':
+ index += 1
+ else:
+ return failure
+
+ success, index, expression = _expression_parser(index, tokens)
+
+ if not success:
+ raise Exception()
+
+ return (
+ True,
+ index,
+ FurSymbolExpressionPair(
+ symbol=symbol,
+ expression=expression,
+ ),
+ )
+
+def _structure_literal_parser(index, tokens):
+ success, index, result = _parenthese_wrapped_parser(_comma_separated_list_parser(symbol_expression_pair_parser))(index, tokens)
+ return (
+ success,
+ index,
+ FurStructureLiteralExpression(
+ fields=result,
+ ),
+ )
+
+def _lambda_expression_parser(index, tokens):
+ failure = (False, index, None)
+
+ if tokens[index].type == 'keyword' and tokens[index].match == 'lambda':
+ index += 1
+ else:
+ return failure
+
+ if tokens[index].type == 'open_parenthese':
+ index += 1
+ else:
+ raise Exception('Expected "(", found "{}" on line {}'.format(
+ tokens[index].match,
+ tokens[index].metadata.line,
+ ))
+
+ success, index, argument_name_list = _comma_separated_list_parser(_symbol_expression_parser)(
+ index,
+ tokens,
+ )
+
+ if tokens[index].type == 'close_parenthese':
+ index += 1
+ else:
+ raise Exception('Expected ")", found "{}" on line {}'.format(
+ tokens[index].match,
+ tokens[index].line,
+ ))
+
+ if tokens[index].match == 'do':
+ index += 1
+ else:
+ return failure
+
+ success, index, statement_list = _zero_or_more_parser(tuple, _statement_parser)(index, tokens)
+
+ _, index, _ = consume_newlines(index, tokens)
+
+ if tokens[index].type == 'keyword' and tokens[index].match == 'end':
+ index += 1
+ else:
+ return failure
+
+ return True, index, FurLambdaExpression(
+ argument_name_list=tuple(an.symbol for an in argument_name_list),
+ statement_list=statement_list,
+ )
+
+
+
+def _list_literal_expression_parser(index, tokens):
+ failure = (False, index, None)
+
+ success, index, item_expression_list = _bracket_wrapped_parser(_comma_separated_expression_list_parser)(index, tokens)
+
+ if success:
+ return success, index, FurListLiteralExpression(
+ item_expression_list=item_expression_list,
+ )
+ else:
+ return failure
+
+def _literal_level_expression_parser(index, tokens):
+ return _or_parser(
+ _list_item_expression_parser,
+ _function_call_expression_parser,
+ _parenthesized_expression_parser,
+ _integer_literal_expression_parser,
+ _string_literal_expression_parser,
+ _list_literal_expression_parser,
+ _lambda_expression_parser,
+ _symbol_expression_parser,
+ _structure_literal_parser,
+ )(index, tokens)
+
+def _dot_expression_parser(index, tokens):
+ return _left_recursive_infix_operator_parser(
+ lambda token: token.type == 'period',
+ _literal_level_expression_parser,
+ 'dot_level',
+ )(index, tokens)
+
+def _negation_expression_parser(index, tokens):
+ failure = (False, index, None)
+
+ if tokens[index].match != '-':
+ return failure
+
+ metadata = tokens[index].metadata
+
+ success, index, value = _dot_expression_parser(index + 1, tokens)
+
+ if not success:
+ return failure
+
+ return (True, index, FurNegationExpression(metadata=metadata, value=value))
+
+def _negation_level_expression_parser(index, tokens):
+ return _or_parser(
+ _dot_expression_parser,
+ _negation_expression_parser,
+ )(index, tokens)
+
+def _left_recursive_infix_operator_parser(operator_token_matcher, operand_parser, order):
+ def result_parser(index, tokens):
+ failure = (False, index, None)
+
+ success, index, result = operand_parser(index, tokens)
+
+ if not success:
+ return failure
+
+ while success and index < len(tokens) and operator_token_matcher(tokens[index]):
+ success = False
+
+ if index + 1 < len(tokens):
+ success, try_index, value = operand_parser(index + 1, tokens)
+
+ if success:
+ result = FurInfixExpression(
+ metadata=tokens[index].metadata,
+ order=order,
+ operator=tokens[index].match,
+ left=result,
+ right=value,
+ )
+ index = try_index
+
+ return True, index, result
+
+ return result_parser
+
+def _multiplication_level_expression_parser(index, tokens):
+ return _left_recursive_infix_operator_parser(
+ lambda token: token.type == 'multiplication_level_operator',
+ _negation_level_expression_parser,
+ 'multiplication_level',
+ )(index, tokens)
+
+def _addition_level_expression_parser(index, tokens):
+ return _left_recursive_infix_operator_parser(
+ lambda token: token.type == 'addition_level_operator',
+ _multiplication_level_expression_parser,
+ 'addition_level',
+ )(index, tokens)
+
+def _comparison_level_expression_parser(index, tokens):
+ return _left_recursive_infix_operator_parser(
+ lambda token: token.type == 'comparison_level_operator',
+ _addition_level_expression_parser,
+ 'comparison_level',
+ )(index, tokens)
+
+def _and_level_expression_parser(index, tokens):
+ return _left_recursive_infix_operator_parser(
+ lambda token: token.type == 'symbol' and token.match == 'and',
+ _comparison_level_expression_parser,
+ 'and_level',
+ )(index, tokens)
+
+def _or_level_expression_parser(index, tokens):
+ return _left_recursive_infix_operator_parser(
+ lambda token: token.type == 'symbol' and token.match == 'or',
+ _and_level_expression_parser,
+ 'or_level',
+ )(index, tokens)
+
+def _comma_separated_list_parser(subparser):
+ def result_parser(index, tokens):
+ start_index = index
+
+ items = []
+
+ _, index, _ = consume_newlines(index, tokens)
+
+ success, index, item = subparser(index, tokens)
+
+ if success:
+ items.append(item)
+ else:
+ return (True, start_index, ())
+
+ while success and index < len(tokens) and tokens[index].type == 'comma':
+ index += 1
+ success = False
+
+ _, index, _ = consume_newlines(index, tokens)
+
+ if index < len(tokens):
+ success, try_index, item = subparser(index, tokens)
+
+ if success:
+ items.append(item)
+ index = try_index
+
+ return True, index, tuple(items)
+
+ return result_parser