On Fri, Jun 21, 2013 at 4:14 PM, Timothee Cour <thelastmammoth@gmail.com> wrote:
On Fri, Jun 21, 2013 at 4:02 PM, Ali Çehreli <acehreli@yahoo.com> wrote:
On 06/21/2013 03:57 PM, Diggory wrote:
On Friday, 21 June 2013 at 22:56:04 UTC, Andrei Alexandrescu wrote:
On 6/21/13 3:55 PM, Andrei Alexandrescu wrote:
On 6/21/13 3:45 PM, Timothee Cour wrote:
I'd like to support N-ary map, ie std.algorithm.map that takes 1 or
more
ranges as arguments and operates lazily on those.

You can use "zip" from std.range.

Timothee specifically said that he is trying to avoid zip: :)


> before:
>   zip(a,b).map!(u=>absDiff(u[0],u[1])).reduce!fun;
> after:
>   map!absDiff(a,b).reduce!fun;

Ali

also works great with string lambdas:
eg: dotproduct:

before:
  zip(u,v).map!"a[0]*a[1]".reduce!"a+b";
after:
  map!"a*b"(u,v).reduce!"a+b";

=> clearer, and provides more room for optimizaton



actually the version without the proposed N-ary map is even worse, because zip uses StoppingPolicy.shortest by default (which i find weird and contrary to D's safe by default stance):

here's the (corrected) dotproduct:

before:
  zip(StoppingPolicy.requireSameLength,u,v).map!"a[0]*a[1]".reduce!"a+b";
after:
  map!"a*b"(u,v).reduce!"a+b";

i think it's a clear improvement in terms of clarity (and again, optimizations possible).