350 lines
8.3 KiB
Python
350 lines
8.3 KiB
Python
# Copyright 2016 Google Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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import collections
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import inspect
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import sys
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import typing
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from . import lex
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class TokenStream:
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def __init__(self, tokens: typing.List[lex.Token]) -> None:
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self.tokens = tokens
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self.at = -1
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def log(self, token: lex.Token):
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calls = inspect.stack()
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context = calls[0][1]
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names = []
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for call in calls:
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if call[1] == context:
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name = call[3]
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if name.startswith('parse_'):
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name = name[6:]
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names.append(name)
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else:
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break
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def advance(self) -> None:
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self.at += 1
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def peek(self, offset: int) -> lex.Token:
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return self.tokens[self.at + offset]
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def prev(self) -> lex.Token:
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return self.tokens[self.at - 1]
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def accept(self, *vals, nolog=False):
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token = self.tokens[self.at]
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for val in vals:
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if isinstance(val, str):
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match = (token.val == val)
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else:
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match = isinstance(token, val)
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if match:
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self.advance()
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if not nolog:
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self.log(token)
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return token
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return None
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def expect(self, *vals):
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tokens = []
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for val in vals:
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token = self.accept(val, nolog=True)
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if not token:
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assert False, 'Parse error: expected {}, got {}'.format(
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repr(val), self.tokens[self.at])
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tokens.append(token)
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self.log(token)
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if len(tokens) == 1:
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return tokens[0]
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else:
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return tokens
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class Node:
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def __init__(self):
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self.children = collections.OrderedDict()
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def set(self, name, value):
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setattr(self, name, value)
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self.children[name] = value
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def append(self, *vals):
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for value in vals:
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self.set('_{}'.format(len(self.children)), value)
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def dump(self, name='', indent=0):
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print('// {}{}: {}'.format(' ' * indent, name, self))
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for name, child in self.children.items():
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if child and isinstance(child, Node):
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child.dump(name, indent + 1)
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else:
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print('// {}{}: {}'.format(' ' * (indent + 1), name, child))
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def typename(self):
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return self.__class__.__name__.lower()
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class Consts(Node, dict):
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pass
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class Vars(Node, dict):
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pass
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class List(Node):
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def __init__(self, items):
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super().__init__()
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for item in items:
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self.append(item)
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class Block(Node):
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pass
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class Program(Node):
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def __init__(self, block):
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super().__init__()
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self.set('block', block)
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class Statement(Node):
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pass
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class Assign(Statement):
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def __init__(self, ident, expr):
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super().__init__()
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self.set('ident', ident)
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self.set('expr', expr)
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class Call(Statement):
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def __init__(self, ident):
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super().__init__()
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self.set('ident', ident)
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class Write(Statement):
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def __init__(self, expression):
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super().__init__()
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self.set('expression', expression)
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class While(Statement):
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def __init__(self, condition, statement):
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super().__init__()
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self.set('condition', condition)
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self.set('statement', statement)
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class If(Statement):
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def __init__(self, condition, statement):
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super().__init__()
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self.set('condition', condition)
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self.set('statement', statement)
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class Odd(Node):
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def __init__(self, expression):
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super().__init__()
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self.set('expression', expression)
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class Condition(Node):
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def __init__(self, left, code, right):
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super().__init__()
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self.set('left', left)
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self.set('code', code)
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self.set('right', right)
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class Procedures(Node):
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pass
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class Procedure(Node):
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pass
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class Expression(Node):
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pass
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class Term(Node):
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pass
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def parse_consts(stream):
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consts = Consts()
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name, _, value = stream.expect(lex.Ident, '=', lex.Number)
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consts[name] = value
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while stream.accept(','):
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name, _, value = stream.expect(lex.Ident, '=', lex.Number)
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consts[name] = value
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stream.expect(';')
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return consts
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def parse_vars(stream):
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variables = Vars()
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name = stream.expect(lex.Ident)
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variables[name] = True
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while stream.accept(','):
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name = stream.expect(lex.Ident)
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variables[name] = True
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stream.expect(';')
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return variables
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class Compound(Statement):
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def __init__(self, statements):
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super().__init__()
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for statement in statements:
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self.append(statement)
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def parse_factor(stream):
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term = stream.accept(lex.Ident, lex.Number)
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if term:
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return term
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stream.expect('(')
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expression = parse_expression(stream)
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stream.expect(')')
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return expression
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def parse_term(stream):
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term = Term()
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factors, operations = [], []
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factors.append(parse_factor(stream))
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while stream.accept('*', '/'):
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operations.append(stream.prev())
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factors.append(parse_factor(stream))
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term.set('factors', List(factors))
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term.set('operations', List(operations))
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return term
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def parse_expression(stream):
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expression = Expression()
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expression.set('unary', stream.accept('+', '-'))
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terms, operations = [], []
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terms.append(parse_term(stream))
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while stream.accept('+', '-'):
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operations.append(stream.prev())
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terms.append(parse_term(stream))
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expression.set('terms', List(terms))
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expression.set('operations', List(operations))
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return expression
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def parse_compound(stream):
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statements = [parse_statement(stream)]
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while stream.accept(';'):
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statements.append(parse_statement(stream))
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stream.expect('end')
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return Compound(statements)
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def parse_condition(stream):
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if stream.accept('odd'):
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return Odd(parse_expression(stream))
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return Condition(
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parse_expression(stream),
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stream.expect(lex.Token), parse_expression(stream))
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def parse_statement(stream):
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if stream.accept(lex.Ident):
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stream.expect(':=')
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return Assign(stream.peek(-2), parse_expression(stream))
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if stream.accept('call'):
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return Call(stream.expect(lex.Ident))
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if stream.accept('!'):
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return Write(parse_expression(stream))
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if stream.accept('begin'):
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return parse_compound(stream)
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if stream.accept('if'):
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cond, _, statement = parse_condition(stream), stream.expect(
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'then'), parse_statement(stream)
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return If(cond, statement)
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if stream.accept('while'):
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cond, _, statement = parse_condition(stream), stream.expect(
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'do'), parse_statement(stream)
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return While(cond, statement)
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return None
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def parse_procedure(stream):
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procedure = Procedure()
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name, _ = stream.expect(lex.Ident, ';')
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block = parse_block(stream)
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stream.expect(';')
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procedure.set('name', name.val)
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procedure.set('block', block)
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return procedure
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def parse_block(stream):
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block = Block()
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if stream.accept('const'):
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block.set('consts', parse_consts(stream))
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else:
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block.set('consts', Consts())
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if stream.accept('var'):
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block.set('vars', parse_vars(stream))
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else:
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block.set('vars', Vars())
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procedures = Procedures()
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while stream.accept('procedure'):
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procedure = parse_procedure(stream)
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procedures.set(procedure.name, procedure)
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block.set('procedures', procedures)
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block.set('statement', parse_statement(stream))
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return block
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def parse(tokens):
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stream = TokenStream(list(tokens))
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stream.advance()
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block, _ = parse_block(stream), stream.expect('.')
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return Program(block)
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def main():
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ast = parse(lex.lex(sys.stdin.read()))
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ast.dump('top')
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if __name__ == '__main__':
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main()
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