A Class in Composition

[John Colvin]

On Tuesday, 27 August 2013 at 14:13:25 UTC, Chris wrote:
> Another drawback is that ranges demand a lot of boilerplate 
> code. If properly implemented, there is a lot of code you have 
> to write over and over again such as
>
> if (isInputRange!Range && isInputRange!(ElementType!Range) &&
>         is(ElementType!(ElementType!Range) == MyType))
>
> I don't know if this could possibly be reduced. Or maybe it's 
> just my lack of experience.

If you've got a lot of repeated template constraints, simply 
moving them out in to a separate template can be useful e.g.

template isIRofIRofT(Range, T)
{
     enum isRoRoT = isInputRange!Range
                 && isInputRange!(ElementType!Range)
                 && is(ElementType!(ElementType!Range) == T);
}

if(isIRofIRofT!(Range, MyType))