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def curry(_curried_func, *args, **kwargs):
def _curried(*moreargs, **morekwargs):
return _curried_func(*(args+moreargs), **dict(kwargs, **morekwargs))
return _curried
class Promise(object):
"""
This is just a base class for the proxy class created in
the closure of the lazy function. It can be used to recognize
promises in code.
"""
pass
def lazy(func, *resultclasses):
"""
Turns any callable into a lazy evaluated callable. You need to give result
classes or types -- at least one is needed so that the automatic forcing of
the lazy evaluation code is triggered. Results are not memoized; the
function is evaluated on every access.
"""
class __proxy__(Promise):
# This inner class encapsulates the code that should be evaluated
# lazily. On calling of one of the magic methods it will force
# the evaluation and store the result. Afterwards, the result
# is delivered directly. So the result is memoized.
def __init__(self, args, kw):
self.__func = func
self.__args = args
self.__kw = kw
self.__dispatch = {}
for resultclass in resultclasses:
self.__dispatch[resultclass] = {}
for (k, v) in resultclass.__dict__.items():
setattr(self, k, self.__promise__(resultclass, k, v))
if unicode in resultclasses:
self.__unicode__ = self.__unicode_cast
self._delegate_str = str in resultclasses
def __promise__(self, klass, funcname, func):
# Builds a wrapper around some magic method and registers that magic
# method for the given type and method name.
def __wrapper__(*args, **kw):
# Automatically triggers the evaluation of a lazy value and
# applies the given magic method of the result type.
res = self.__func(*self.__args, **self.__kw)
return self.__dispatch[type(res)][funcname](res, *args, **kw)
if klass not in self.__dispatch:
self.__dispatch[klass] = {}
self.__dispatch[klass][funcname] = func
return __wrapper__
def __unicode_cast(self):
return self.__func(*self.__args, **self.__kw)
def __str__(self):
# As __str__ is always a method on the type (class), it is looked
# up (and found) there first. So we can't just assign to it on a
# per-instance basis in __init__.
if self._delegate_str:
return str(self.__func(*self.__args, **self.__kw))
else:
return Promise.__str__(self)
def __wrapper__(*args, **kw):
# Creates the proxy object, instead of the actual value.
return __proxy__(args, kw)
return __wrapper__
def allow_lazy(func, *resultclasses):
"""
A decorator that allows a function to be called with one or more lazy
arguments. If none of the args are lazy, the function is evaluated
immediately, otherwise a __proxy__ is returned that will evaluate the
function when needed.
"""
def wrapper(*args, **kwargs):
for arg in list(args) + kwargs.values():
if isinstance(arg, Promise):
break
else:
return func(*args, **kwargs)
return lazy(func, *resultclasses)(*args, **kwargs)
return wrapper
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