Simple template constraint question

[anonymous via Digitalmars-d-learn]

On Saturday 19 September 2015 19:09, WhatMeWorry wrote:

> And a more open ended question.  Is there a more elegant solution 
> for the
> below function?  Maybe a one-liner?  I have a knack for making 
> simple solutions
> complex :)
> 
> 
> 
> // Calculate the number of components for openGL generic
> // vertex attribute. Must be 1, 2, 3, 4.
> 
> // isAggregateType constraint accepts class, union, struct, and 
> interface
> 
> int getNumberComponents(T)(T someStruct) if (isAggregateType!(T))
> {
>      int members = 0;
>      foreach (i, member; someStruct.tupleof)
>      {
>          //writefln("Member %s:", i);
>          //writefln("  type : %s", typeof(member).stringof);
>          //writefln("  value: %s", member);
>          members++;
>      }
>      return members;
> }

If the whole goal is to get how many members T has:
----
template getNumberComponents(T) if (is(T == struct))
{
    enum getNumberComponents = T.tupleof.length;
}
----

Or you can write `T.tupleof.length` directly, of course.