opDispatch(string name, E...) (E e) question.

[Simen Kjærås]

On Sun, 25 Mar 2012 22:45:57 +0200, bls <bizprac at orange.fr> wrote:

> How do I "call" opDispatch(string name, E...)(E elements) ?
> What I want to archive is to call f.i. fm.list with an arbitrary number  
> of arguments without using
>
> fm.list(1, "abc", 4L, 3.33);
>
> Instead I would prefer
> fm.list = (1, "abc", 4L, 3.33);
>
> Is this somehow possible ?

No. However, this is:

fm.list = tuple( 1, "abc", 4L, 3.33 );

In that case, you probably want to use the overload
opDispatch(string name, E...)(Tuple!E elements)

and mark the other:
opDispatch(string name, E...)(E element) if ( !(E.length == 1 &&  
isTuple!(E[0])))

tuple, Tuple, and isTuple are found in std.typecons.


> import std.variant;
> import std.conv;
> ....
> auto fm = FlexMap();
>
> fm.ten = 10;
> fm.ten = ["Ten", "Zehn", "Tein"];
> fm.list = [20, 10, 2, 2, 44 ] ;
> fm.list = "Hello opDispatch";
>
> struct FlexMap
> {
>      Variant[] [string] map;
>
>      Variant[] opDispatch(string name)()
>      {
>         return map[name];
>      }
> 	
>      Variant[] opDispatch(string name, E...)(E elements)
>      {
> 	foreach(element; elements)
>         		map[name] ~= to!Variant(element);
>         	return map[name];
>      }
> 	
>      Variant[] opDispatch(string name, T) (T t)
>      {
> 	map[name] ~= to!Variant(t);
> 	return map[name];
>      }		
> }
>
>
>
> Another question :
> How do I bring in :
>
> opDispatch(string name, T) (T[] t)
>
> into FlexMap ?


It's possible to do with template constraints:

import std.traits : isArray;

void opDispatch(string name, T)(T t) if ( isArray!T )
{
     // Array specific.
}
void opDispatch(string name, T)(T t) if ( !isArray!T)
{
     // Single element.
}



One could also use static if:

Variant[] opDispatch(string name, T)(T t)
{
     static if ( is( T U : U[] ) )
     {
         map[name] ~= to!
     }
     else
     {
         // Whatever you want to do differently here.
     }
}