import collections
-StringLiteral = collections.namedtuple(
- 'StringLiteral',
+def consume_newlines(index, tokens):
+ while index < len(tokens) and tokens[index].type == 'newline':
+ index += 1
+
+ return True, index, None
+
+def _or_parser(*parsers):
+ def result_parser(index, tokens):
+ failure = (False, index, None)
+
+ for parser in parsers:
+ success, index, value = parser(index, tokens)
+
+ if success:
+ return (success, index, value)
+
+ return failure
+
+ return result_parser
+
+def _zero_or_more_parser(formatter, parser):
+ def result_parser(index, tokens):
+ values = []
+
+ while index < len(tokens):
+ success, index, value = parser(index, tokens)
+
+ if success:
+ values.append(value)
+ else:
+ break
+
+ return (True, index, formatter(values))
+
+ return result_parser
+
+FurIntegerLiteralExpression = collections.namedtuple(
+ 'FurIntegerLiteralExpression',
+ [
+ 'integer',
+ ],
+)
+
+FurStringLiteralExpression = collections.namedtuple(
+ 'FurStringLiteralExpression',
+ [
+ 'string',
+ ],
+)
+
+FurSymbolExpression = collections.namedtuple(
+ 'FurSymbolExpression',
[
'value',
],
)
-def _string_literal_parser(index, tokens):
+FurNegationExpression = collections.namedtuple(
+ 'FurNegationExpression',
+ [
+ 'value',
+ ],
+)
+
+FurInfixExpression = collections.namedtuple(
+ 'FurInfixExpression',
+ [
+ 'order',
+ 'operator',
+ 'left',
+ 'right',
+ ],
+)
+
+def _integer_literal_expression_parser(index, tokens):
failure = (False, index, None)
- if tokens[index].type != 'single_quoted_string_literal':
+ if tokens[index].type != 'integer_literal':
return failure
- value = tokens[index].match[1:-1]
+ value = int(tokens[index].match)
index += 1
- return True, index, StringLiteral(value=value)
+ return True, index, FurIntegerLiteralExpression(integer=value)
+
+def _string_literal_expression_parser(index, tokens):
+ if tokens[index].type == 'single_quoted_string_literal':
+ return (True, index + 1, FurStringLiteralExpression(string=tokens[index].match[1:-1]))
+
+ return (False, index, None)
+
+def _symbol_expression_parser(index, tokens):
+ if tokens[index].type == 'symbol':
+ return (True, index + 1, FurSymbolExpression(value=tokens[index].match))
+
+ return (False, index, None)
+
+def _parenthese_wrapped_parser(internal_parser):
+ def result_parser(index, tokens):
+ failure = (False, index, None)
+
+ if tokens[index].type == 'open_parenthese':
+ index += 1
+ else:
+ return failure
+
+ success, index, internal = internal_parser(index, tokens)
+ if not success:
+ return failure
+
+ if tokens[index].type == 'close_parenthese':
+ index += 1
+ else:
+ raise Exception('Expected ")" on line {}, found "{}"'.format(
+ tokens[index].line,
+ tokens[index].match,
+ ))
+
+ return True, index, internal
+
+ return result_parser
+
+def _parenthesized_expression_parser(index, tokens):
+ return _parenthese_wrapped_parser(_expression_parser)(index, tokens)
+
+def _negation_expression_parser(index, tokens):
+ failure = (False, index, None)
+
+ if tokens[index].match != '-':
+ return failure
+
+ success, index, value = _literal_level_expression_parser(index + 1, tokens)
+
+ if not success:
+ return failure
+
+ return (True, index, FurNegationExpression(value=value))
+
+def _literal_level_expression_parser(index, tokens):
+ return _or_parser(
+ _negation_expression_parser,
+ _function_call_expression_parser,
+ _parenthesized_expression_parser,
+ _integer_literal_expression_parser,
+ _string_literal_expression_parser,
+ _symbol_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(
+ 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',
+ _literal_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 = []
+
+ 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':
+ success = False
+
+ if index + 1 < len(tokens):
+ success, try_index, item = subparser(index + 1, tokens)
+ if success:
+ items.append(item)
+ index = try_index
-FunctionCall = collections.namedtuple(
- 'FunctionCall',
+ return True, index, tuple(items)
+
+ return result_parser
+
+def _comma_separated_expression_list_parser(index, tokens):
+ return _comma_separated_list_parser(_expression_parser)(index, tokens)
+
+FurFunctionCallExpression = collections.namedtuple(
+ 'FurFunctionCallExpression',
[
- 'name',
+ 'function',
'arguments',
],
)
-def _function_call_parser(index, tokens):
+FurExpressionStatement = collections.namedtuple(
+ 'FurExpressionStatement',
+ [
+ 'expression',
+ ],
+)
+
+FurAssignmentStatement = collections.namedtuple(
+ 'FurAssignmentStatement',
+ [
+ 'target',
+ 'expression',
+ ],
+)
+
+FurFunctionDefinitionStatement = collections.namedtuple(
+ 'FurFunctionDefinitionStatement',
+ [
+ 'name',
+ 'argument_name_list',
+ 'statement_list',
+ ],
+)
+
+FurProgram = collections.namedtuple(
+ 'FurProgram',
+ [
+ 'statement_list',
+ ],
+)
+
+def _function_call_expression_parser(index, tokens):
failure = (False, index, None)
- if tokens[index].type != 'symbol':
+ # We have to be careful what expressions we add here. Otherwise expressions
+ # like "a + b()" become ambiguous to the parser.
+ success, index, function = _or_parser(
+ _symbol_expression_parser,
+ _parenthesized_expression_parser,
+ )(index, tokens)
+
+ if not success:
return failure
- name = tokens[index].match
- index += 1
- if tokens[index].type != 'open_parenthese':
+ success, index, arguments = _parenthese_wrapped_parser(_comma_separated_expression_list_parser)(
+ index,
+ tokens,
+ )
+
+ if not success:
+ return failure
+
+ while success and index < len(tokens):
+ # "function" is actually the full function call if the next parse attempt doesn't succeed
+ # We can't give this a better name without a bunch of checks, however.
+ function = FurFunctionCallExpression(
+ function=function,
+ arguments=arguments,
+ )
+
+ success, index, arguments = _parenthese_wrapped_parser(_comma_separated_expression_list_parser)(
+ index,
+ tokens,
+ )
+
+ return True, index, function
+
+_expression_parser = _or_level_expression_parser
+
+def _expression_statement_parser(index, tokens):
+ failure = (False, index, None)
+
+ success, index, expression = _expression_parser(index, tokens)
+
+ if not success:
+ return failure
+
+ 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
- index += 1
- success, index, argument = _string_literal_parser(index, tokens)
+
+ 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 != 'close_parenthese':
+ 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:
+ raise Exception('Expected ")", found "{}" on line {}'.format(
+ tokens[index].match,
+ tokens[index].line,
+ ))
+
+ if tokens[index].type == 'symbol' and 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
- index += 1
-
- return True, index, FunctionCall(name=name, arguments=(argument,))
+
+ return True, index, FurFunctionDefinitionStatement(
+ name=name,
+ argument_name_list=tuple(an.value for an in argument_name_list),
+ statement_list=statement_list,
+ )
+
+def _statement_parser(index, tokens):
+ _, index, _ = consume_newlines(index, tokens)
+
+ if index == len(tokens):
+ return (False, index, None)
+
+ return _or_parser(
+ _assignment_statement_parser,
+ _expression_statement_parser,
+ _function_definition_statement_parser,
+ )(index, tokens)
+
+def _program_formatter(statement_list):
+ return FurProgram(statement_list=statement_list)
+
+_program_parser = _zero_or_more_parser(_program_formatter, _statement_parser)
def _parse(parser, tokens):
success, index, result = parser(0, tokens)
+ if index < len(tokens):
+ raise Exception('Unable to parse token {}'.format(tokens[index]))
+
if success:
return result
raise Exception('Unable to parse')
-
def parse(tokens):
- return _parse(_function_call_parser, tokens)
+ return _parse(_program_parser, tokens)
if __name__ == '__main__':
import unittest
import tokenization
- class StringLiteralParserTests(unittest.TestCase):
+ class FurStringLiteralExpressionParserTests(unittest.TestCase):
def test_parses_single_quoted_string_literal(self):
self.assertEqual(
- _string_literal_parser(0, tokenization.tokenize("'Hello, world'")),
+ _string_literal_expression_parser(0, tokenization.tokenize("'Hello, world'")),
(
True,
1,
- StringLiteral(value='Hello, world'),
+ FurStringLiteralExpression(string='Hello, world'),
),
)
- class FunctionCallParserTests(unittest.TestCase):
+ class FurFunctionCallExpressionParserTests(unittest.TestCase):
def test_parses_function_with_string_literal_argument(self):
self.assertEqual(
- _function_call_parser(0, tokenization.tokenize("print('Hello, world')")),
+ _function_call_expression_parser(0, tokenization.tokenize("print('Hello, world')")),
(
True,
4,
- FunctionCall(
+ FurFunctionCallExpression(
name='print',
- arguments=(StringLiteral(value='Hello, world'),),
+ arguments=(FurStringLiteralExpression(string='Hello, world'),),
),
),
)