Andrei Alexandrescu wrote:
Sergey Gromov wrote:
Sat, 24 Jan 2009 17:09:07 -0800, Andrei Alexandrescu wrote:
I'm working on the new range stuff and the range-based algorithm. In
all likelihood, you all might be pleased with the results.
I wanted to gauge opinions on a couple of issues. One is, should the
empty() member function for ranges be const? On the face of it it
should, but I don't want that to be a hindrance. I presume non-const
empty might be necessary sometimes, e.g. figuring out if a stream is
empty effectively means fetching an element off it.
I have a hard time imagining a use for a const range.
Read-only arrays for example.
A range is essentially an iterator. It has to change its internal state
to move to the next element. So a const range will not allow you to
iterate over the members of a const array. It will allow you to iterate
over a single element, either once or an infinite number of times.
You could change ranges to have "Range next()" rather than "void
next()", and that would allow you to use a const Range for reasons other
than checking whether it's empty. Iterating over a range would then look
like:
for (auto range = getRange(); !range.empty; range = range.next) {}
I don't see much purpose to this. If you want polymorphic ranges, you're
going to use a class for ranges. This will incur a lot of allocations,
which will be dog slow. The current design would only allocate once if
your range is a class.
