Partially instantiating templates?

[Simen kjaeraas]

Andrej Mitrovic <andrej.mitrovich at gmail.com> wrote:

> On 1/31/11, Simen kjaeraas <simen.kjaras at 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