On Thursday, 1 October 2015 at 04:08:00 UTC, bitwise wrote:
I understand, but the C++ committee seems very conservative to
me, so when it's this easy to add for(:) support by giving
ranges begin()/end() functions, it makes me doubt they will
actually change the language for it.
As of C++11, C++ has the for(auto e:range) control structure you
are looking for. I would be using it here except for one thing:
in my proposal, begin() and end() don't have to return objects of
the same type! begin() must return an iterator and end() must
return something that is EqualityComparable with the iterator --
but it doesn't have to be an iterator. That makes many types of
iterators vastly simpler to implement and more efficient at
runtime.
C++'s built-in range-based for(:) loop expects begin() and end()
to return objects of the same type. The committee is already
talking about loosening that constraint so that the ranges I'm
proposing Just Work with the existing built-in looping construct.
Until then, there is an ugly macro. It's a temporary hack,
nothing more.
Hope that clears things up.
Eric
P.S. I see lots of people here assuming that C++ is playing
catch-up to D because D has ranges and C++ doesn't yet. That is
ignoring the long history of ranges in C++. C++ got ranges in the
form of the Boost.Range library by Thorsten Ottoson sometime in
the early 00's. Andrei didn't implement D's ranges until many
years after. The ranges idea is older than dirt. It's not a D
invention.
