PEP 309 (Partial Function Application) Idea

[Reinhold Birkenfeld]

Steven Bethard wrote:
> Chris Perkins wrote:
>> Random idea of the day: How about having syntax support for
>> currying/partial function application, like this:
>> 
>> func(..., a, b)
>> func(a, ..., b)
>> func(a, b, ...)
>> 
>> That is:
>> 1) Make an Ellipsis literal legal syntax in an argument list.
>> 2) Have the compiler recognize the Ellipsis literal and transform the
>> function call into a curried/parially applied function.
>> 
>> So the compiler would essentially do something like this:
>> 
>> func(a, ...) ==> curry(func, a)
>> func(..., a) ==> rightcurry(func, a)
>> func(a, ..., b) ==> rightcurry(curry(func,a), b)
>> 
>> I haven't though this through much, and I'm sure there are issues, but
>> I do like the way it looks.  The "..." really stands out as saying
>> "something is omitted here".
> 
> Interesting idea, but I have a feeling that it probably won't fly for a 
> couple of reasons:
> 
> (1) The existing use of Ellipsis doesn't have anything to do with your 
> suggested use.  I think people are generally opposed to giving 
> keywords/symbols in Python two very different meanings.  This is one of 
> the reasons Guido never liked the "a, b, *c = iterable" syntax.
> 
> (2) Emphasis recently on python-dev has been away from syntax changes 
> and towards expansion of the standard library.  You would have to make a 
> _very_ good case that the new syntax is merited.
> 
> Generally I do like the idea -- I think a lot of the cases that people 
> have made for keeping lambda could be discarded with something like 
> this...  But it'd need an extremely well thought out PEP (and an 
> implementation of course) and even then, I wouldn't get my hopes up.

I like it, and if it helps to convince people that it is okay to get rid
of lambda, perhaps Guido will like it too.

What about proposing it on python-dev?

Reinhold