Re: [Caml-list] C++ STL and template features compared with OCaml parametric polymorphism and OO features

[Radu Grigore <radugrigore@gmail.com>]

On Sun, 26 Sep 2004 19:51:52 +0100, Jon Harrop <jon@jdh30.plus.com> wrote:
> > Nope. That only works for a limited class algorithms.
> > Try a map function.. woops, you can't type it .. :)

> Yes you can:
> # let vec_add map2 = map2 ( +. );;
> val vec_add : ((float -> float -> float) -> 'a) -> 'a = <fun>
> 
> So you can then do:
> 
> # let list_add = vec_add List.map2;;
> val list_add : float list -> float list -> float list = <fun>
> 
> I think you're thinking of a function to convert between 'a and 'b container
> types.

I think the idea is that you can't write a _generic_ map. All you did
above is a dipatcher that gives the job to a specialized map function:
List.map2. The accumulate function in C++ is not a simple dispatcher.
It can implement the logic of "fold" because there is an extra level
of abstraction: iterators.

But what John says is possible in FISh (namely, writing a generic,
shape preserving map) sounds quite cool.

regards,
 radu
"Get your data structures correct first and the rest of the program
will write itself." – David Jones.
http://rgrig.idilis.ro/

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