How to expand an expression along with a parameter tuple?

[TommiT]

On Tuesday, 18 June 2013 at 10:57:00 UTC, Artur Skawina wrote:
> On 06/18/13 03:51, TommiT wrote:
>> Change the call to bar(1, 3L); and it wouldn't even compile.
>> It's because all the types of _ForEach.tuple are the same as 
>> the first element of TS...
>> 
>> I mean... the same as the type of MAP(TS[0])
>
> That was enough to handle the original problem, iirc.
> Making the code work for heterogeneous args (and mapping 
> functions) is
> trivial, though:
>
>    import std.stdio;
>
>    template _TypeMap(alias MAP, size_t N, TS...) {
>        static if (N<TS.length)
>            alias _TypeMap = _TypeMap!(MAP, N+1, TS[0..N], 
> typeof(MAP(TS[N].init), TS[N..$]));
>        else
>            alias _TypeMap = TS;
>    }
>    template TypeMap(alias MAP, TS...) {
>       alias TypeMap = _TypeMap!(MAP, 0, TS);
>    }
>
>    struct _ForEach(alias MAP, TS...)
>    {
>        TypeMap!(MAP, TS) tuple;
>
>        this(TS values)
>        {
>            foreach (i, ref v; values)
>                tuple[i] = MAP(v);
>        }
>    }
>
>    auto ForEach(alias MAP, TS...)(TS ts)
>    {
>        return _ForEach!(MAP, TS)(ts);
>    }
>
>    void foo(T...)(T values)
>    {
>        foreach (v; values)
>            writeln(v);
>    }
>
>    void bar(T...)(T values)
>    {
>        foo(ForEach!(a => a + 1)(values).tuple);
>    }
>
>    void main()
>    {
>        bar(10, 3_000_000_000u, 2.14, -43L);
>    }
>
>
> artur

Okay, you really seem to have figured this stuff out. I think I 
have difficulty seeing the solution because I'm used to C++ 
parameter packs, which have much less functionality than 
parameter tuples in D + there's no static if. But I learned a lot 
from this, thanks for that.