RFC on range design for D2

[Sean Kelly]

Andrei Alexandrescu wrote:
> 
> Then there remains the problem:
> 
> void bump(R, V)(R r)
> {
>     for (; !r.isEmpty; r.next) ++r.first;
> }
> 
> bump(charArraySucker); // bogus
> 
> Sigh...

And I suppose you don't want to return a const reference from first() 
because the user may want to operate on the value, if only on a 
temporary basis?  Let's say:

P findFirst(P, R, C)( R r, C c )
{
     for( ; !r.isEmpty; r.next )
     {
         // modify the temporary because a new element is expensive
         // to copy-construct
         if( auto p = c.contains( ++r.first ) )
             return p;
     }
     return P.init;
}

Hm... must the implementation prevent stupid mistakes such as your 
example?  Ideally, yes.  But I don't see a way to do so and yet allow 
for routines like findFirst() above.


Sean