diff options
Diffstat (limited to 'src/parser.py')
| -rw-r--r-- | src/parser.py | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/src/parser.py b/src/parser.py new file mode 100644 index 0000000..5ee5207 --- /dev/null +++ b/src/parser.py @@ -0,0 +1,196 @@ +# Copyright 2015 Egor Tensin <Egor.Tensin@gmail.com> +# This file is licensed under the terms of the MIT License. +# See LICENSE.txt for details. + +from lexer import * +from nodes import * + +class ParserError(RuntimeError): + pass + +class Parser: + def __init__(self, src_file): + self._lexer = Lexer(src_file) + + def parse(self): + return self._parse_program() + + def _try_parse_token(self, cls): + if not self._lexer.has_next_token(): + return False + t = self._lexer.preview_next_token() + if not isinstance(t, cls): + return False + self._lexer.drop_next_token() + return t + + def _parse_token(self, cls): + if not self._lexer.has_next_token(): + raise ParserError("%s expected" % cls.__name__) + t = self._lexer.preview_next_token() + if not isinstance(t, cls): + raise ParserError("%s expected instead of %s" % ( + cls.__name__, t.__class__.__name__)) + self._lexer.drop_next_token() + return t + + def _parse_program(self): + stmt_list = [] + while self._lexer.has_next_token(): + stmt = self._try_parse_stmt() + if not stmt: + raise ParserError("unexpected token '%s'" % ( + self._lexer.preview_next_token())) + stmt_list.append(stmt) + return ProgramNode(stmt_list) + + def _try_parse_stmt(self): + print_stmt = self._try_parse_print_stmt() + if print_stmt: + return print_stmt + assignment = self._try_parse_assignment() + if assignment: + return assignment + empty_stmt = self._try_parse_empty_stmt() + if empty_stmt: + return empty_stmt + if_stmt = self._try_parse_if_stmt() + if if_stmt: + return if_stmt + block = self._try_parse_block() + if block: + return block + return False + + def _try_parse_empty_stmt(self): + if not self._try_parse_token(SemicolonToken): + return False + return EmptyStatementNode() + + def _try_parse_block(self): + if not self._try_parse_token(OpeningBraceToken): + return False + stmt_list = [] + while True: + stmt = self._try_parse_stmt() + if stmt: + stmt_list.append(stmt) + else: + break + self._parse_token(ClosingBraceToken) + return CompoundStatementNode(stmt_list) + + def _try_parse_if_stmt(self): + if not self._try_parse_token(IfToken): + return False + self._parse_token(OpeningParenToken) + cond = self._parse_logical_expr() + self._parse_token(ClosingParenToken) + stmt = self._try_parse_stmt() + if not stmt: + raise ParserError("unexpected token '%s'" % ( + self._lexer.preview_next_token())) + return IfStatementNode(cond, stmt) + + def _try_parse_print_stmt(self): + if not self._try_parse_token(PrintToken): + return False + arithm_expr = self._parse_arithm_expr() + self._parse_token(SemicolonToken) + return PrintStatementNode(arithm_expr) + + def _try_parse_assignment(self): + if not self._lexer.has_next_token(2): + return False + identifier = self._lexer.preview_next_token(0) + if not isinstance(identifier, IdentifierToken): + return False + op = self._lexer.preview_next_token(1) + if not isinstance(op, AssignmentOpToken): + return False + self._lexer.drop_next_token(2) + arithm_expr = self._parse_arithm_expr() + self._parse_token(SemicolonToken) + return AssignmentNode(identifier, arithm_expr) + + def _parse_logical_expr(self): + left = self._parse_logical_term() + while self._lexer.has_next_token(): + if self._try_parse_token(AndOpToken): + left = AndOpNode(left, self._parse_logical_term()) + elif self._try_parse_token(OrOpToken): + left = OrOpNode(left, self._parse_logical_term()) + else: + return left + return left + + def _parse_logical_term(self): + left = self._parse_logical_factor() + if self._lexer.has_next_token(): + if self._try_parse_token(EqualsOpToken): + left = EqualsOpNode(left, self._parse_logical_factor()) + elif self._try_parse_token(NotEqualsOpToken): + left = NotEqualsOpNode(left, self._parse_logical_factor()) + else: + return left + return left + + def _parse_logical_factor(self): + if self._try_parse_token(TrueToken): + return TrueNode() + elif self._try_parse_token(FalseToken): + return FalseNode() + elif self._try_parse_token(OpeningParenToken): + logical_expr = self._parse_logical_expr() + self._parse_token(ClosingParenToken) + return logical_expr + else: + raise ParserError('expected \'True\', \'False\' or \'(\'') + + def _parse_arithm_expr(self): + left = self._parse_arithm_term() + while self._lexer.has_next_token(): + if self._try_parse_token(AdditionOpToken): + left = AdditionOpNode(left, self._parse_arithm_term()) + elif self._try_parse_token(SubtractionOpToken): + left = SubtractionOpNode(left, self._parse_arithm_term()) + else: + return left + return left + + def _parse_arithm_term(self): + left = self._parse_arithm_factor() + while self._lexer.has_next_token(): + if self._try_parse_token(MultiplicationOpToken): + left = MultiplicationOpNode(left, self._parse_arithm_factor()) + elif self._try_parse_token(DivisionOpToken): + left = DivisionOpNode(left, self._parse_arithm_factor()) + else: + return left + return left + + def _parse_arithm_factor(self): + identifier = self._try_parse_token(IdentifierToken) + if identifier: + return IdentifierNode(identifier) + int_num = self._try_parse_token(IntegerNumberToken) + if int_num: + return IntegerNumberNode(int_num) + float_num = self._try_parse_token(FloatingPointNumberToken) + if float_num: + return FloatingPointNumberNode(float_num) + if self._try_parse_token(OpeningParenToken): + arithm_expr = self._parse_arithm_expr() + self._parse_token(ClosingParenToken) + return arithm_expr + else: + raise ParserError('expected an identifier, a number or \'(\'') + +if __name__ == '__main__': + import argparse + parser = argparse.ArgumentParser() + parser.add_argument('src_path', help='set source file path') + args = parser.parse_args() + with open(args.src_path, 'r') as src_file: + parser = Parser(src_file) + parser.parse().execute() |