Re: Partially instantiating templates?

[Simen kjaeraas]

Andrej Mitrovic <andrej.mitrov...@gmail.com> wrote:

On 1/31/11, Simen kjaeraas <simen.kja...@gmail.com> wrote:

module foo;

import std.typecons;
import std.functional;
import std.array;

template optArg( alias pred ) {
     template optArg( alias fn ) {
         auto optArg( Range )( Range r ) {
             alias binaryFun!pred predicate;
             alias unaryFun!fn func;

             auto result = tuple( r.front, func( r.front ) );
             foreach ( e; r ) {
                 auto tmp = func( e );
                 if ( predicate( e, result[1] ) ) {
                     result = tuple( e, tmp );
                 }
             }
             return result;
         }
     }
}

void main( ) {
     alias optArg!"a<b" minArg;
     alias minArg!"a" foo;
     assert( foo( [5,2,1,3] ) == tuple(1,1) );
}

Damn! That's pretty nice, I didn't know we could nest with the
eponymous trick. This could be quite useful, thanks.

You can only do that using aliases.

--
Simen