currying at language level (was: Re: add_command)

[holger krekel]

Alex Martelli wrote:
> I'd love to have built-in currying, but the syntax
> sugar you propose is clearly too limited (e.g., how
> does it apply to keyword-arguments?)

does it need to? IOW what problems do you expect?
i think the usual TypeErrors when e.g. supplying multiple
values for an argument are straight forward to come up
with.

> (is currying important enough to
> deserve special syntax, and, if so, what is the right
> sugar for it?)

There are some good reasons IMO for making it a syntax thing
but first the concepts, agreed.

> A more sensible, gradualistic
> approach might be to look for consensus on the exact
> functionality that can be encapsulated in a built-in,
> or even as a curry function that might be part of a
> new FP module -- _that_ one we might stand a chance to
> get into the standard library, perhaps.  If and when
> currying becomes so popular as to deserve its own
> special syntax sugar, then it may be a better time to
> debate the details of that sugar.

yes. Only it is not so easy to get even a
builtin to provide 'enough' convenience. Consider one of 
my currying implementations which does it like so:

f1=PrebindFunc(f, BINDLATER, 2, BINDLATER, karg1="hehe")

But how can you get around the special name 'BINDLATER'? 
Take 'XXX'? Somehow it doesn't seem right to me to
try to makeup a name. Not unless there is a standardization 
on ONE name which is hard to achieve.

> > IMHO currying is a well-understood concept
> 
> It sure is _in a specific way_, the one analyzed and
> widely used by Dr Haskell Curry: applying a function
> f (which you could consider an "N-argument function"
> in traditional terms) to an argument a to yield a new
> anonymous function which you could consider an "N-1
> argument function" in traditional terms.

I don't know haskell, sorry, but just currying the 
leftmost arguments is quite restrictive and doesn't
fit to python's functio model IMO.

> But this doesn't mean we know exactly what should be
> done in presence of named/optional arguments and other
> cases of variadic functions.  "Currying the 1st and
> 3rd args of a 3-argument functions" is also a somewhat
> unexplored realm AFAIK.

If people knew how to do it and if it were easy to type
they'd like it, i guess. Wouldn't you? 

It may be *a bit* like with 'yield'. Once you get it you 
don't want to live without it. But you didn't know before. 
Or maybe _you_ did :-)

    holger