Make sub_match a proper range

[zeratul976@…]

boost::xpressive::sub_match comes close to being a proper Range, but it's not quite. It has a nested type named 'iterator', but not one named 'const_iterator', and it lacks begin() and end() functions.

It should be very straightforward to add these missing bits and make it a proper range. Alternately, it could derive from boost::iterator_range<BidiIter> rather than std::pair<BidiIter, BidiIter>.

[Eric Niebler]

xpressive's sub_match is closely modeled on std::sub_match, which doesn't have the members you refer to. But xpressive doesn't slavishly follow the standard, and what you suggest is reasonable. I would prefer to non-intrusively make sub_match a valid range by hooking Boost.Range's customization points.

But would sub_match's const_iterator be a typedef for iterator, or would it const-ify the iterator (if necessary)? And do I need rbegin/rend, cbegin/cend, crbegin/crend and the associated typedefs, too? Sheesh! Opinions?

[zeratul976@…]

xpressive's sub_match is closely modeled on std::sub_match, which doesn't have the members you refer to

Right, because ranges haven't been fully standardized. I expect that when they are, care will be taken to make things like std::sub_match be a Range.

I would prefer to non-intrusively make sub_match a valid range by hooking Boost.Range's customization points.

That's reasonable.

would sub_match's const_iterator be a typedef for iterator, or would it const-ify the iterator (if necessary)?

const_iterator should be the type returned when calling begin() on a 'const sub_match', so the answer depends on whether you think it should be allowed to modify the string through a 'const sub_match'. I have no strong feelings either way.

And do I need rbegin/rend, cbegin/cend, crbegin/crend and the associated typedefs, too?

No. Those members are required by the standard Container concept, which is a (large) superset of the Range concept. I am not proposing that sub_match model Container.

Thanks! Nate

[Eric Niebler]

Fixed on trunk in [80300]. I've taken the boost::iterator_range and std::pair route and kept const_iterator the same as iterator. Thanks!

[Eric Niebler]

Fixed on release in [80581]. Will be part of Boost 1.52.

[Michel Morin]

begin/end member functions might be better, since they also support C++11 range-based for.