Add .vimrc file. Some cleanup, formatting and comments
This commit is contained in:
Eli Bendersky
parent
824d7ecd44
commit
de4efda63c
3 changed files with 12 additions and 3 deletions
461
chapter2.py
461
chapter2.py
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@ -1,461 +0,0 @@
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# Chapter 1&2 - Lexer and Parser
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from collections import namedtuple
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from enum import Enum
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# Each token is a tuple of kind and value. kind is one of the enumeration values
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# in TokenKind. value is the textual value of the token in the input.
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class TokenKind(Enum):
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EOF = -1
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DEF = -2
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EXTERN = -3
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IDENTIFIER = -4
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NUMBER = -5
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OPERATOR = -6
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Token = namedtuple('Token', 'kind value')
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class Lexer(object):
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"""Lexer for Kaleidoscope.
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Initialize the lexer with a string buffer. tokens() returns a generator that
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can be queried for tokens. The generator will emit an EOF token before
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stopping.
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"""
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def __init__(self, buf):
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assert len(buf) >= 1
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self.buf = buf
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self.pos = 0
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self.lastchar = self.buf[0]
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def tokens(self):
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while self.lastchar:
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# Skip whitespace
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while self.lastchar.isspace():
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self._advance()
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# Identifier or keyword
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if self.lastchar.isalpha():
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id_str = ''
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while self.lastchar.isalnum():
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id_str += self.lastchar
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self._advance()
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if id_str == 'def':
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yield Token(kind=TokenKind.DEF, value=id_str)
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elif id_str == 'extern':
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yield Token(kind=TokenKind.EXTERN, value=id_str)
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else:
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yield Token(kind=TokenKind.IDENTIFIER, value=id_str)
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# Number
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elif self.lastchar.isdigit() or self.lastchar == '.':
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num_str = ''
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while self.lastchar.isdigit() or self.lastchar == '.':
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num_str += self.lastchar
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self._advance()
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yield Token(kind=TokenKind.NUMBER, value=num_str)
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# Comment
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elif self.lastchar == '#':
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self._advance()
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while self.lastchar and self.lastchar not in '\r\n':
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self._advance()
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elif self.lastchar:
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# Some other char
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yield Token(kind=TokenKind.OPERATOR, value=self.lastchar)
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self._advance()
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yield Token(kind=TokenKind.EOF, value='')
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def _advance(self):
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try:
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self.pos += 1
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self.lastchar = self.buf[self.pos]
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except IndexError:
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self.lastchar = ''
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# AST hierarchy
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class ASTNode(object):
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def dump(self, indent=0):
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raise NotImplementedError
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class ExprAST(ASTNode):
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pass
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class NumberExprAST(ExprAST):
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def __init__(self, val):
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self.val = val
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def dump(self, indent=0):
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return '{0}{1}[{2}]'.format(
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' ' * indent, self.__class__.__name__, self.val)
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class VariableExprAST(ExprAST):
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def __init__(self, name):
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self.name = name
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def dump(self, indent=0):
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return '{0}{1}[{2}]'.format(
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' ' * indent, self.__class__.__name__, self.name)
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class BinaryExprAST(ExprAST):
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def __init__(self, op, lhs, rhs):
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self.op = op
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self.lhs = lhs
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self.rhs = rhs
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def dump(self, indent=0):
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s = '{0}{1}[{2}]\n'.format(
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' ' * indent, self.__class__.__name__, self.op)
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s += self.lhs.dump(indent + 2) + '\n'
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s += self.rhs.dump(indent + 2)
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return s
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class CallExprAST(ExprAST):
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def __init__(self, callee, args):
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self.callee = callee
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self.args = args
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def dump(self, indent=0):
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s = '{0}{1}[{2}]\n'.format(
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' ' * indent, self.__class__.__name__, self.callee)
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for arg in self.args:
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s += arg.dump(indent + 2) + '\n'
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return s[:-1] # snip out trailing '\n'
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class PrototypeAST(ASTNode):
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def __init__(self, name, argnames):
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self.name = name
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self.argnames = argnames
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def dump(self, indent=0):
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return '{0}{1}[{2}]'.format(
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' ' * indent, self.__class__.__name__, ', '.join(self.argnames))
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class FunctionAST(ASTNode):
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def __init__(self, proto, body):
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self.proto = proto
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self.body = body
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def dump(self, indent=0):
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s = '{0}{1}[{2}]\n'.format(
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' ' * indent, self.__class__.__name__, self.proto.dump())
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s += self.body.dump(indent + 2) + '\n'
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return s
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class ParseError(Exception): pass
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class Parser(object):
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"""Parser for the Kaleidoscope language.
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After the parser is created, invoke parse_toplevel multiple times to parse
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Kaleidoscope source into an AST.
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"""
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def __init__(self):
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self.token_generator = None
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self.cur_tok = None
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# toplevel ::= definition | external | expression | ';'
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def parse_toplevel(self, buf):
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"""Given a string, returns an AST node representing it."""
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self.token_generator = Lexer(buf).tokens()
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self.cur_tok = None
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self._get_next_token()
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if self.cur_tok.kind == TokenKind.EXTERN:
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return self._parse_external()
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elif self.cur_tok.kind == TokenKind.DEF:
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return self._parse_definition()
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elif self._cur_tok_is_operator(';'):
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self._get_next_token()
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return None
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else:
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return self._parse_toplevel_expression()
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def _get_next_token(self):
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self.cur_tok = next(self.token_generator)
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def _match(self, expected_kind, expected_value=None):
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"""Consume the current token; verify that it's of the expected kind.
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If expected_kind == TokenKind.OPERATOR, verify the operator's value.
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"""
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if (expected_kind == TokenKind.OPERATOR and
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not self._cur_tok_is_operator(expected_value)):
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raise ParseError('Expected "{0}"'.format(expected_value))
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elif expected_kind != self.cur_tok.kind:
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raise ParseError('Expected "{0}"'.format(expected_kind))
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self._get_next_token()
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_precedence_map = {'<': 10, '+': 20, '-': 20, '*': 40}
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def _cur_tok_precedence(self):
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"""Get the operator precedence of the current token."""
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try:
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return Parser._precedence_map[self.cur_tok.value]
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except KeyError:
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return -1
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def _cur_tok_is_operator(self, op):
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"""Query whether the current token is the operator op"""
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return (self.cur_tok.kind == TokenKind.OPERATOR and
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self.cur_tok.value == op)
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# identifierexpr
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# ::= identifier
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# ::= identifier '(' expression* ')'
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def _parse_identifier_expr(self):
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id_name = self.cur_tok.value
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self._get_next_token()
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# If followed by a '(' it's a call; otherwise, a simple variable ref.
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if not self._cur_tok_is_operator('('):
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return VariableExprAST(id_name)
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self._get_next_token()
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args = []
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if not self._cur_tok_is_operator(')'):
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while True:
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args.append(self._parse_expression())
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if self._cur_tok_is_operator(')'):
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break
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self._match(TokenKind.OPERATOR, ',')
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self._get_next_token() # consume the ')'
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return CallExprAST(id_name, args)
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# numberexpr ::= number
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def _parse_number_expr(self):
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result = NumberExprAST(self.cur_tok.value)
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self._get_next_token() # consume the number
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return result
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# parenexpr ::= '(' expression ')'
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def _parse_paren_expr(self):
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self._get_next_token() # consume the '('
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expr = self._parse_expression()
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self._match(TokenKind.OPERATOR, ')')
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return expr
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# primary
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# ::= identifierexpr
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# ::= numberexpr
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# ::= parenexpr
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def _parse_primary(self):
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if self.cur_tok.kind == TokenKind.IDENTIFIER:
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return self._parse_identifier_expr()
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elif self.cur_tok.kind == TokenKind.NUMBER:
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return self._parse_number_expr()
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elif self._cur_tok_is_operator('('):
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return self._parse_paren_expr()
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else:
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raise ParseError('Unknown token when expecting an expression')
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# binoprhs ::= (<binop> primary)*
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def _parse_binop_rhs(self, expr_prec, lhs):
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"""Parse the right-hand-side of a binary expression.
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expr_prec: minimal precedence to keep going (precedence climbing).
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lhs: AST of the left-hand-side.
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"""
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while True:
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cur_prec = self._cur_tok_precedence()
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# If this is a binary operator with precedence lower than the
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# currently parsed sub-expression, bail out. If it binds at least
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# as tightly, keep going.
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# Note that the precedence of non-operators is defined to be -1,
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# so this condition handles cases when the expression ended.
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if cur_prec < expr_prec:
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return lhs
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op = self.cur_tok.value
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self._get_next_token() # consume the operator
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rhs = self._parse_primary()
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next_prec = self._cur_tok_precedence()
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# There are three options:
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# 1. next_prec > cur_prec: we need to make a recursive call
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# 2. next_prec == cur_prec: no need for a recursive call, the next
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# iteration of this loop will handle it.
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# 3. next_prec < cur_prec: no need for a recursive call, combine
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# lhs and the next iteration will immediately bail out.
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if cur_prec < next_prec:
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rhs = self._parse_binop_rhs(cur_prec + 1, rhs)
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# Merge lhs/rhs
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lhs = BinaryExprAST(op, lhs, rhs)
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# expression ::= primary binoprhs
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def _parse_expression(self):
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lhs = self._parse_primary()
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# Start with precedence 0 because we want to bind any operator to the
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# expression at this point.
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return self._parse_binop_rhs(0, lhs)
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# prototype ::= id '(' id* ')'
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def _parse_prototype(self):
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name = self.cur_tok.value
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self._match(TokenKind.IDENTIFIER)
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self._match(TokenKind.OPERATOR, '(')
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argnames = []
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while self.cur_tok.kind == TokenKind.IDENTIFIER:
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argnames.append(self.cur_tok.value)
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self._get_next_token()
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self._match(TokenKind.OPERATOR, ')')
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return PrototypeAST(name, argnames)
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# external ::= 'extern' prototype
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def _parse_external(self):
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self._get_next_token() # consume 'extern'
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return self._parse_prototype()
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# definition ::= 'def' prototype expression
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def _parse_definition(self):
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self._get_next_token() # consume 'def'
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proto = self._parse_prototype()
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expr = self._parse_expression()
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return FunctionAST(proto, expr)
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# toplevel ::= expression
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def _parse_toplevel_expression(self):
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expr = self._parse_expression()
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# Anonymous function
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return FunctionAST(PrototypeAST('', []), expr)
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#---- Some unit tests ----#
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import unittest
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class TestLexer(unittest.TestCase):
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def _assert_toks(self, toks, kinds):
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"""Assert that the list of toks has the given kinds."""
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self.assertEqual([t.kind.name for t in toks], kinds)
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def test_lexer_simple_tokens_and_values(self):
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l = Lexer('a+1')
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toks = list(l.tokens())
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self.assertEqual(toks[0], Token(TokenKind.IDENTIFIER, 'a'))
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self.assertEqual(toks[1], Token(TokenKind.OPERATOR, '+'))
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self.assertEqual(toks[2], Token(TokenKind.NUMBER, '1'))
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self.assertEqual(toks[3], Token(TokenKind.EOF, ''))
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l = Lexer('.1519')
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toks = list(l.tokens())
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self.assertEqual(toks[0], Token(TokenKind.NUMBER, '.1519'))
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def test_token_kinds(self):
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l = Lexer('10.1 def der extern foo (')
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self._assert_toks(
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list(l.tokens()),
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['NUMBER', 'DEF', 'IDENTIFIER', 'EXTERN', 'IDENTIFIER',
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'OPERATOR', 'EOF'])
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l = Lexer('+- 1 2 22 22.4 a b2 C3d')
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self._assert_toks(
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list(l.tokens()),
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['OPERATOR', 'OPERATOR', 'NUMBER', 'NUMBER', 'NUMBER', 'NUMBER',
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'IDENTIFIER', 'IDENTIFIER', 'IDENTIFIER', 'EOF'])
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def test_skip_whitespace_comments(self):
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l = Lexer('''
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def foo # this is a comment
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# another comment
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\t\t\t10
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''')
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self._assert_toks(
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list(l.tokens()),
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['DEF', 'IDENTIFIER', 'NUMBER', 'EOF'])
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class TestParser(unittest.TestCase):
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def _flatten(self, ast):
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"""Test helper - flattens the AST into a sexpr-like nested list."""
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if isinstance(ast, NumberExprAST):
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return ['Number', ast.val]
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elif isinstance(ast, VariableExprAST):
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return ['Variable', ast.name]
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elif isinstance(ast, BinaryExprAST):
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return ['Binop', ast.op,
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self._flatten(ast.lhs), self._flatten(ast.rhs)]
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elif isinstance(ast, CallExprAST):
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args = [self._flatten(arg) for arg in ast.args]
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return ['Call', ast.callee, args]
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elif isinstance(ast, PrototypeAST):
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return ['Proto', ast.name, ' '.join(ast.argnames)]
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elif isinstance(ast, FunctionAST):
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return ['Function',
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self._flatten(ast.proto), self._flatten(ast.body)]
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else:
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raise TypeError('unknown type in _flatten: {0}'.format(type(ast)))
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def _assert_body(self, toplevel, expected):
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"""Assert the flattened body of the given toplevel function"""
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self.assertIsInstance(toplevel, FunctionAST)
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self.assertEqual(self._flatten(toplevel.body), expected)
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def test_basic(self):
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ast = Parser().parse_toplevel('2')
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self.assertIsInstance(ast, FunctionAST)
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self.assertIsInstance(ast.body, NumberExprAST)
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self.assertEqual(ast.body.val, '2')
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def test_basic_with_flattening(self):
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ast = Parser().parse_toplevel('2')
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self._assert_body(ast, ['Number', '2'])
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ast = Parser().parse_toplevel('foobar')
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self._assert_body(ast, ['Variable', 'foobar'])
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def test_expr_singleprec(self):
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ast = Parser().parse_toplevel('2+ 3-4')
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self._assert_body(ast,
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['Binop',
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'-', ['Binop', '+', ['Number', '2'], ['Number', '3']],
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['Number', '4']])
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def test_expr_multiprec(self):
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ast = Parser().parse_toplevel('2+3*4-9')
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self._assert_body(ast,
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['Binop', '-',
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['Binop', '+',
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['Number', '2'],
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['Binop', '*', ['Number', '3'], ['Number', '4']]],
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['Number', '9']])
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def test_expr_parens(self):
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ast = Parser().parse_toplevel('2*(3-4)*7')
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self._assert_body(ast,
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['Binop', '*',
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['Binop', '*',
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['Number', '2'],
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['Binop', '-', ['Number', '3'], ['Number', '4']]],
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['Number', '7']])
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def test_externals(self):
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ast = Parser().parse_toplevel('extern sin(arg)')
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self.assertEqual(self._flatten(ast), ['Proto', 'sin', 'arg'])
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ast = Parser().parse_toplevel('extern Foobar(nom denom abom)')
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self.assertEqual(self._flatten(ast),
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['Proto', 'Foobar', 'nom denom abom'])
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def test_funcdef(self):
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ast = Parser().parse_toplevel('def foo(x) 1 + bar(x)')
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self.assertEqual(self._flatten(ast),
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['Function', ['Proto', 'foo', 'x'],
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['Binop', '+',
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['Number', '1'],
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['Call', 'bar', [['Variable', 'x']]]]])
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if __name__ == '__main__':
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p = Parser()
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print(p.parse_toplevel('def bina(a b) a + b').dump())
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