How to map elements of a tuple?

[Simen Kjærås]

On Wednesday, 22 August 2018 at 10:36:32 UTC, Andrey wrote:
> Hello,
> Is there a template/function/mixin... in the library that I can 
> use to map elements of a tuple?
>
>> object.foo(Mapper!myMapFunction(1, bool, "Qwerty", 
>> EnumedColor.Red));
>
> where "Mapper" is this mapper and "myMapFunction" is a template 
> function that I want to apply to each member in tuple.
>
> I know that there is std.algorithm.map but as I understand it 
> is suitable only for arrays (types are the same).

I believe this should be what you're looking for:

import std.typecons;

auto map(alias fn, T...)(Tuple!T arg) {
     import std.conv : text;
     import std.range : iota;
     import std.algorithm.iteration : joiner, map;

     return mixin(text("tuple(",T.length.iota.map!(i => 
text("fn(arg[",i,"])")).joiner(", "),")"));
}

unittest {
     import std.conv : to;
     auto a = tuple(1,2,"").map!(a => a.to!string);
     assert(a == tuple("1","2",""));
}

--
   Simen