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import tokenize
import string
def parse_signature(sig):
'''Parse generalized ufunc signature.
NOTE: ',' (COMMA) is a delimiter; not separator.
This means trailing comma is legal.
'''
def stripws(s):
return ''.join(c for c in s if c not in string.whitespace)
def tokenizer(src):
def readline():
yield src
gen = readline()
return tokenize.generate_tokens(lambda: next(gen))
def parse(src):
tokgen = tokenizer(src)
while True:
tok = next(tokgen)
if tok[1] == '(':
symbols = []
while True:
tok = next(tokgen)
if tok[1] == ')':
break
elif tok[0] == tokenize.NAME:
symbols.append(tok[1])
elif tok[1] == ',':
continue
else:
raise ValueError('bad token in signature "%s"' % tok[1])
yield tuple(symbols)
tok = next(tokgen)
if tok[1] == ',':
continue
elif tokenize.ISEOF(tok[0]):
break
elif tokenize.ISEOF(tok[0]):
break
else:
raise ValueError('bad token in signature "%s"' % tok[1])
ins, _, outs = stripws(sig).partition('->')
inputs = list(parse(ins))
outputs = list(parse(outs))
# check that all output symbols are defined in the inputs
isym = set()
osym = set()
for grp in inputs:
isym |= set(grp)
for grp in outputs:
osym |= set(grp)
diff = osym.difference(isym)
if diff:
raise NameError('undefined output symbols: %s' % ','.join(sorted(diff)))
return inputs, outputs
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