[phobos] D std.bind

[Jason Spencer]

Andrei Alexandrescu <andrei at ...> writes:
> 
> I wrote a curry in std.functional which I think could be a good starting 
> point.

I'm new to D syntax, but if I read that right, std.curry just gives you
an alias to a function call of two variables that fills in one for
you.  Deprecating bind would still leave holes for:

- Currying an arbitrary length parameter list
- storing a delegate to the curried function
- composing curries (could be replaced by previous 2 if done in a certain way)
- binding at arbitrary parameter indexes

and maybe a couple of other things.  In short, bind gives support for all kinds of 
partial applications, where as std.curry only allows picking off one arg in a 
two-arg function.  If bind were deprecated, is there a plan to replace the other 
functionality?

Seems like with the new functional capabilities of D 2, bind is MORE
necessary, since I would imagine more higher order functions being
written and extended.  If that's true, then there's gonna be an awful
lot of boiler plate code like:

   auto p_2 = function ReturnType!plus (ParameterTypeTuple!plus[1] arg2,
   ParameterTypeTuple!plus[2] arg3) { return plus(2, arg2, arg3); } ;

rather than

   auto p_2 = bind(plus, 2, _0, _1);

I'd love to see partial applications supported in the language, but short of 
that, I'd say there needs to be some easier way to curry in, say 5 argument 
calls, or else the functional features of D really loose
power. Bind already provides that.  Maybe it just needs a make-over?

Jason