130 lines
5.0 KiB
Python
130 lines
5.0 KiB
Python
def curry(_curried_func, *args, **kwargs):
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def _curried(*moreargs, **morekwargs):
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return _curried_func(*(args+moreargs), **dict(kwargs, **morekwargs))
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return _curried
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def memoize(func, cache, num_args):
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"""
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Wrap a function so that results for any argument tuple are stored in
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'cache'. Note that the args to the function must be usable as dictionary
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keys.
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Only the first num_args are considered when creating the key.
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"""
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def wrapper(*args):
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mem_args = args[:num_args]
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if mem_args in cache:
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return cache[mem_args]
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result = func(*args)
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cache[mem_args] = result
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return result
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return wrapper
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class Promise(object):
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"""
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This is just a base class for the proxy class created in
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the closure of the lazy function. It can be used to recognize
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promises in code.
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"""
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pass
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def lazy(func, *resultclasses):
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"""
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Turns any callable into a lazy evaluated callable. You need to give result
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classes or types -- at least one is needed so that the automatic forcing of
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the lazy evaluation code is triggered. Results are not memoized; the
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function is evaluated on every access.
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"""
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class __proxy__(Promise):
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# This inner class encapsulates the code that should be evaluated
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# lazily. On calling of one of the magic methods it will force
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# the evaluation and store the result. Afterwards, the result
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# is delivered directly. So the result is memoized.
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def __init__(self, args, kw):
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self.__func = func
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self.__args = args
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self.__kw = kw
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self.__dispatch = {}
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for resultclass in resultclasses:
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self.__dispatch[resultclass] = {}
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for (k, v) in resultclass.__dict__.items():
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setattr(self, k, self.__promise__(resultclass, k, v))
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self._delegate_str = str in resultclasses
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self._delegate_unicode = unicode in resultclasses
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assert not (self._delegate_str and self._delegate_unicode), "Cannot call lazy() with both str and unicode return types."
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if self._delegate_unicode:
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# Each call to lazy() makes a new __proxy__ object, so this
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# doesn't interfere with any other lazy() results.
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__proxy__.__unicode__ = __proxy__.__unicode_cast
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elif self._delegate_str:
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__proxy__.__str__ = __proxy__.__str_cast
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def __promise__(self, klass, funcname, func):
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# Builds a wrapper around some magic method and registers that magic
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# method for the given type and method name.
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def __wrapper__(*args, **kw):
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# Automatically triggers the evaluation of a lazy value and
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# applies the given magic method of the result type.
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res = self.__func(*self.__args, **self.__kw)
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return self.__dispatch[type(res)][funcname](res, *args, **kw)
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if klass not in self.__dispatch:
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self.__dispatch[klass] = {}
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self.__dispatch[klass][funcname] = func
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return __wrapper__
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def __unicode_cast(self):
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return self.__func(*self.__args, **self.__kw)
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def __str_cast(self):
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return str(self.__func(*self.__args, **self.__kw))
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def __cmp__(self, rhs):
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if self._delegate_str:
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s = str(self.__func(*self.__args, **self.__kw))
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elif self._delegate_unicode:
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s = unicode(self.__func(*self.__args, **self.__kw))
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else:
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s = self.__func(*self.__args, **self.__kw)
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if isinstance(rhs, Promise):
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return -cmp(rhs, s)
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else:
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return cmp(s, rhs)
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def __mod__(self, rhs):
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if self._delegate_str:
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return str(self) % rhs
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elif self._delegate_unicode:
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return unicode(self) % rhs
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else:
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raise AssertionError('__mod__ not supported for non-string types')
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def __deepcopy__(self, memo):
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# Instances of this class are effectively immutable. It's just a
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# collection of functions. So we don't need to do anything
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# complicated for copying.
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memo[id(self)] = self
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return self
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def __wrapper__(*args, **kw):
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# Creates the proxy object, instead of the actual value.
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return __proxy__(args, kw)
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return __wrapper__
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def allow_lazy(func, *resultclasses):
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"""
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A decorator that allows a function to be called with one or more lazy
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arguments. If none of the args are lazy, the function is evaluated
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immediately, otherwise a __proxy__ is returned that will evaluate the
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function when needed.
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"""
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def wrapper(*args, **kwargs):
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for arg in list(args) + kwargs.values():
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if isinstance(arg, Promise):
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break
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else:
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return func(*args, **kwargs)
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return lazy(func, *resultclasses)(*args, **kwargs)
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return wrapper
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