[issue13430] Add a curry function to the functools module
Petri Lehtinen pe...@digip.org added the comment: @markonervo: Have you tried the pointfree library: http://pypi.python.org/pypi/pointfree/ ? I think it's exactly what you're asking for. The only case I've ever needed currying was managing callback soup in async code. And even then, functools.partial() was perfectly enough. I don't think this would be useful in Python stdlib, so -1 from me. -- nosy: +petri.lehtinen ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Collin Winter coll...@gmail.com added the comment: I assume I was added to this thread since I wrote the functional module, so I'll give my take in that capacity. IMO Python doesn't need a more general version of partial(); indeed, I question the need for partial() as it is today. Querying Google Code Search for code using partial, I haven't found any usages in the wild where partial() makes code more readable than simply defining a new function. partial() is almost always a loss for readability. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
New submission from Marko Nervo ma...@python.it: I think it would be very usefull to add a curry function to the functools module. It should be like this. def curry(func, *args, **kwargs): if (len(args) + len(kwargs)) = func.__code__.co_argcount: return func(*args, **kwargs) return (lambda *x, **y: curry(func, *(args + x), **dict(kwargs, **y))) This function allows you to create curried functions or methods in two main ways: (1) def adder(x, y, z): ... return (x + y + z) adder = curry(adder) (2) @curry ... def adder(x, y, z): ... return (x + y + z) Curried functions could be used as follow. adder(2, 3, 4) adder(2, 3)(4) adder(2)(3)(4) adder(z = 4)(2, 3) # etc, etc, etc... Best regards, Marco. -- components: Library (Lib) messages: 147882 nosy: collinwinter, eric.araujo, gregory_p, markonervo, rhettinger, serprex priority: normal severity: normal status: open title: Add a curry function to the functools module type: feature request versions: Python 2.7, Python 3.4 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Ezio Melotti ezio.melo...@gmail.com added the comment: This sounds similar to http://wiki.python.org/moin/PythonDecoratorLibrary#Pseudo-currying Do you have a concrete use case for this? -- nosy: +ezio.melotti versions: +Python 3.3 -Python 2.7, Python 3.4 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Antoine Pitrou pit...@free.fr added the comment: You can use functools.partial for similar effect. Not sure what a dedicated curry() primitive would improve. -- nosy: +pitrou ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Alex Gaynor alex.gay...@gmail.com added the comment: This already exists, as functools.partial: http://docs.python.org/library/functools.html#functools.partial -- nosy: +alex resolution: - invalid status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Marko Nervo ma...@python.it added the comment: In [1]: import functools In [2]: def adder(x, y, z): ...: return (x + y + z) ...: In [3]: adder = functools.partial(adder) In [4]: adder(2)(3)(4) --- TypeError Traceback (most recent call last) /home/marko/ipython console in module() TypeError: adder() takes exactly 3 arguments (1 given) No, it can't be replaced using functools.partial. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Éric Araujo mer...@netwok.org added the comment: To go back to your original message: I think it would be very usefull to add a curry function to the functools module. For what use cases? Curried functions could be used as follow. adder(2, 3, 4) adder(2, 3)(4) adder(2)(3)(4) adder(z = 4)(2, 3) # etc, etc, etc... I don’t know the curry concept from other languages, but I’m experienced with Python and don’t like this idea at all. A function returns something; the returned value being callable or not is a property of that value, not of the function. The examples above look confusing to me. I think you should discuss your use cases on the python-ideas mailing list. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Ezio Melotti ezio.melo...@gmail.com added the comment: FWIW there is a somewhat related thread that proposed a new syntax for curried functions: http://mail.python.org/pipermail/python-ideas/2009-March/003220.html -- stage: - committed/rejected ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Marko Nervo ma...@python.it added the comment: I totally disagree with the syntax for curried function, but I think a curry function is perfect for the functools module and I also think it could be useful at least as functools.partial. In addition, a lot of languages support currying, such as Haskell, Scala, Javascript... However, here an example less confusional adder = curry(lambda (x, y): (x + y)) adder3 = adder(3) adder3(4) 7 adder3(5) 8 Currying let you defining new functions on other functions. This is a common practice in functional programming (point-free style). So, why not? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Antoine Pitrou pit...@free.fr added the comment: However, here an example less confusional adder = curry(lambda (x, y): (x + y)) adder3 = adder(3) adder3(4) 7 adder3(5) 8 Currying let you defining new functions on other functions. But so does functools.partial. So the question is, what use case does it help that functools.partial doesn't? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Ezio Melotti ezio.melo...@gmail.com added the comment: In that thread Guido said: Haskell has this too, perhaps even more extreme: there's not really such a thing in Haskell as a function of N arguments (N 1). f a b = ... defines a function f of one argument a which returns another function (f a) of one argument b. And so on. That doesn't mean we need to copy this idea in Python. New features require a valid use case before being included, and I'm afraid why not? is not valid :) (Also nothing prevents you to define your own curry function/decorator and use it where you need it.) -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Marko Nervo ma...@python.it added the comment: But so does functools.partial. So the question is, what use case does it help that functools.partial doesn't? Sure, it's common `defining new functions on other functions`... more times. Here a stupid example with fold (our reduce). @curry def fold(function, start, sequence): if len(sequence) == 0: return start else: return fold(function, function(start, sequence[0]), sequence[1:]) Now, someone could be define a generic summer function by fold. import operator as op summer = fold(op.add) Now, an other programmer could be use summer for defining listsummer (a function which sum only list), as follow. listsummer = summer([]) In addition, curry is cleaver than functools.partial. summer = functools.partial(fold, op.add) listsummer = functools.partial(summer, []) However, it is an additional feature. Nobody forces you to use it, but if you need it... Yeah, you could rewrite it each time, but why? It is perfect in functools (: -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Antoine Pitrou pit...@free.fr added the comment: Sure, it's common `defining new functions on other functions`... more times. Here a stupid example with fold (our reduce). @curry def fold(function, start, sequence): if len(sequence) == 0: return start else: return fold(function, function(start, sequence[0]), sequence[1:]) Now, someone could be define a generic summer function by fold. import operator as op summer = fold(op.add) Right... so you defined these helper functions (curry, fold) just to... define a generic summer function? Really? I understand that fold() and curry() may look pretty to functional languages people, but they don't solve any real-world problems that Python doesn't already solve in a neater way. You will have to try a bit harder and showcase examples of *useful* code that are made significantly easier through the use of curry(). (no, generic summer functions are *not* real-world use cases. They are homework exercises for CS students, at best) -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13430] Add a curry function to the functools module
Marko Nervo ma...@python.it added the comment: You will have to try a bit harder and showcase examples of *useful* code that are made significantly easier through the use of curry(). Curry is a more advanced functools.partial. So, it could be used *at least* as partial, but it is more powerfull, usable and readable. I think it's a valid reason; if it isn't, I haven't anything else to say. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13430 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
