def read(s):
"""Parse an expression from a string. If the string does not contain an
expression, None is returned. If the string cannot be parsed, a SyntaxError
is raised.
>>> read('lambda f: f(0)')
LambdaExpr(['f'], CallExpr(Name('f'), [Literal(0)]))
>>> read('(lambda x: x)(5)')
CallExpr(LambdaExpr(['x'], Name('x')), [Literal(5)])
>>> read('(lambda: 5)()')
CallExpr(LambdaExpr([], Literal(5)), [])
>>> read('lambda x y: 10')
Traceback (most recent call last):
...
SyntaxError: expected ':' but got 'y'
>>> read(' ') # returns None
"""
src = Buffer(tokenize(s))
if src.current() is not None:
return read_expr(src)
def read(s):
"""Parse an expression from a string. If the string does not contain an
expression, None is returned. If the string cannot be parsed, a SyntaxError
is raised.
>>> read('lambda f: f(0)')
LambdaExpr(['f'], CallExpr(Name('f'), [Literal(0)]))
>>> read('(lambda x: x)(5)')
CallExpr(LambdaExpr(['x'], Name('x')), [Literal(5)])
>>> read('(lambda: 5)()')
CallExpr(LambdaExpr([], Literal(5)), [])
>>> read('lambda x y: 10')
Traceback (most recent call last):
...
SyntaxError: expected ':' but got 'y'
>>> read(' ') # returns None
"""
src = Buffer(tokenize(s))
if src.current() is not None:
return read_expr(src)
def read(s):
src = Buffer(tokenize(s))
if src.current() is not None:
return read_expr(src)
is raised.
>>> read('lambda f: f(0)')
LambdaExpr(['f'], CallExpr(Name('f'), [Literal(0)]))
>>> read('(lambda x: x)(5)')
CallExpr(LambdaExpr(['x'], Name('x')), [Literal(5)])
>>> read('(lambda: 5)()')
CallExpr(LambdaExpr([], Literal(5)), [])
>>> read('lambda x y: 10')
Traceback (most recent call last):
...
SyntaxError: expected ':' but got 'y'
>>> read(' ') # returns None
"""
src = Buffer(tokenize(s))
if src.current() is not None:
return read_expr(src)
###########
## Lexer ##
###########
def tokenize(s):
"""Splits the string s into tokens and returns a list of them.
>>> tokenize('lambda f: f(0, 4.2)')
['lambda', 'f', ':', 'f', '(', 0, ',', 4.2, ')']
"""
src = Buffer(s)
tokens = []
