On Thursday, 27 February 2014 at 21:24:20 UTC, Tobias Pankrath
wrote:
On Thursday, 27 February 2014 at 21:09:45 UTC, Ben Jones wrote:
My question is: which features of the D range abstraction
allow zip to work the way we expect? What C++isms were left
behind to make this work?
Many items in std.algorithm / std.range make use of static if
to provide the most capable return types. I.e. if you zip to RA
ranges than zip will return a random access range, too.
See
https://github.com/D-Programming-Language/phobos/blob/master/std/range.d#L4988
That can be done in C++ too (albeit less elgantly) with tag
dispatch or enable if, or whatever. The big issue I ran into was
dealing with the semantics of iterator dereferencing. I'm not
sure anyone has come up with a way to define an iterator whose
dereference operator returns a reference type when dealing with a
zipped range in C++.
It seems that somehow D's range abstraction avoids that issues
somehow, but I don't quite understand how.
