有确切的替代品吗功能性.curry？

Question

我试图在python2.6运行时上运行http://www.ibm.com/developerworks/linux/library/l-prog3.html中的这段代码。在

from functional import *

taxcalc = lambda income,rate,deduct: (income-(deduct))*rate

taxCurry = curry(taxcalc)
taxCurry = taxCurry(50000)
taxCurry = taxCurry(0.30)
taxCurry = taxCurry(10000)
print "Curried taxes due =",taxCurry

print "Curried expression taxes due =", \
      curry(taxcalc)(50000)(0.30)(10000)

好的，所以我从http://www.python.org/dev/peps/pep-0309/了解到functional被重命名为functools，curry被重命名为partial，但是仅仅重命名没有帮助。我得到了一个错误：

^{pr2}$

下面的方法确实有用，但我真的要改变这么多吗？在

from functools import partial

taxcalc = lambda income,rate,deduct: (income-(deduct))*rate

taxCurry = partial(taxcalc)
taxCurry = partial(taxCurry, 50000)
taxCurry = partial(taxCurry, 0.30)
taxCurry = partial(taxCurry, 10000)
print "Curried taxes due =", taxCurry()

print "Curried expression taxes due =", \
      taxcalc(50000, 0.30, 10000)

有没有更好的方法来保存原始示例的机制？最后，最初的例子是真正的流行还是只是部分应用？（根据http://www.uncarved.com/blog/not_currying.mrk）

谢谢你的时间

Answer 1

我想他们改变它的原因是因为Python是动态类型的。这意味着，如果出现任何错误，调试原始的curry代码将非常困难，这比Haskell这样的语言更难，因为在Haskell中，你会直接得到一个很好的类型错误。{cdthonic的决定看起来更合理。在

您的示例也有点奇怪，因为您只是将部分应用的函数重新指定为相同的名称。通常，部分应用的功能将被赋予另一个功能。至少这是我能想到的Python中唯一合理的用例。在

Answer 2

^{} project中curry的实现应该是一个插入式替换。在

$ pip install toolz
>>> from toolz import curry

Answer 3

我写的an implementation of a curry decorator效果很好：

def curry(func):
    """
    Decorator to curry a function, typical usage:

    >>> @curry
    ... def foo(a, b, c):
    ...    return a + b + c

    The function still work normally:
    >>> foo(1, 2, 3)
    6

    And in various curried forms:
    >>> foo(1)(2, 3)
    6
    >>> foo(1)(2)(3)
    6

    This also work with named arguments:
    >>> foo(a=1)(b=2)(c=3)
    6
    >>> foo(b=1)(c=2)(a=3)
    6
    >>> foo(a=1, b=2)(c=3)
    6
    >>> foo(a=1)(b=2, c=3)
    6

    And you may also change your mind on named arguments,
    But I don't know why you may want to do that:
    >>> foo(a=1, b=0)(b=2, c=3)
    6

    Finally, if you give more parameters than expected, the exception
    is the expected one, not some garbage produced by the currying
    mechanism:

    >>> foo(1, 2)(3, 4)
    Traceback (most recent call last):
       ...
    TypeError: foo() takes exactly 3 arguments (4 given)
    """
    def curried(*args, **kwargs):
        if len(args) + len(kwargs) >= func.__code__.co_argcount:
            return func(*args, **kwargs)
        return (lambda *args2, **kwargs2:
                curried(*(args + args2), **dict(kwargs, **kwargs2)))
    return curried


if __name__ == "__main__":
    import doctest
    doctest.testmod()