#!/usr/bin/env python
from functools import wraps
class InvalidSignature(Exception): pass
def returns(rettype):
def check(ret):
if not isinstance(ret, rettype): raise InvalidSignature()
return ret
def returnchecker(func):
@wraps(func)
def _func(*args, **kwargs):
return check(func(*args, **kwargs))
_func.returns = rettype
return _func
return returnchecker
def signature(*argtypes, **kwtypes):
def check(args, kwargs):
if not len(args) == len(argtypes): raise InvalidSignature()
if not all(isinstance(a, b) for a, b in zip(args, argtypes)): raise InvalidSignature()
if not len(kwargs) == len(kwtypes): raise InvalidSignature()
if not set(kwargs) == set(kwtypes) : raise InvalidSignature()
if not all(isinstance(kwargs[kw], kwtypes[kw]) for kw in kwtypes): raise InvalidSignature()
def typechecker(func):
@wraps(func)
def _func(*args, **kwargs):
check(args, kwargs)
return func(*args, **kwargs)
_func.signature = argtypes, kwtypes
return _func
return typechecker
def overloaded(func):
@wraps(func)
def overloaded_func(*args, **kwargs):
for f in overloaded_func.overloads:
try:
return f(*args, **kwargs)
except (InvalidSignature, TypeError):
pass
else:
raise TypeError("No compatible signatures")
def overload_with(func):
overloaded_func.overloads.append(func)
return overloaded_func
overloaded_func.overloads = [func]
overloaded_func.overload_with = overload_with
return overloaded_func
#############
@overloaded
def a():
print 'no args a'
pass
@a.overload_with
def a(n):
print 'arged a'
pass
a()
a(4)
@overloaded
@returns(int)
@signature(int, int, float)
def foo(a, b, c):
return int(a * b * c)
@foo.overload_with
@returns(int)
@signature(int, float, c=int)
def foo(a, b, c):
return int(a + b + c)
print foo(2, 3, 4.)
print foo(10, 3., c=30)
print foo(1, 9., 3, 3)
