Boost C++ Libraries: Ticket #6683: find family of functions needs const Range1T& Input overloads

status changed

Marshall Clow — Tue, 13 Mar 2012 15:07:24 GMT

status new → assigned

Ok, I'm confused here; the title says "needs const Range1 T& input overloads", but the body talks about having an overload that returns a range.

The search algorithms return a single iterator, not a range. If you look in the file boyer_moore.hpp, there are a set of calls that take ranges. I have to add those calls to the other search algorithms, but I'd appreciate it if you would tell me what you think is lacking there.

anonymous — Tue, 13 Mar 2012 17:51:15 GMT

Sorry. The signature for lets say find_first is:

template<typename Range1T, typename Range2T> inline iterator_range< BOOST_STRING_TYPENAME range_iterator<Range1T>::type > find_first( Range1T& Input, const Range2T& Search )

As Input isn't const it's not possible to pass rvalues. Now, what I speculate is the reason for why it isn't const ( because it would be natural to assume that merely searching would not need to alter the content ), is because iterator_range<> in this case which is returned from the function gives the caller the opportunity to alter Input indirectly through the iterator_range. So, what I propose is something which would have the following signature instead added as an overload:

template<typename Range1T, typename Range2T> inline const_iterator_range< BOOST_STRING_TYPENAME const_range_iterator<Range1T>::type > find_first( const Range1T& Input, const Range2T& Search )

const_iterator_range in this case would serve the same role that const_iterator does compared to iterator in std.

Marshall Clow — Wed, 14 Mar 2012 03:15:31 GMT

Ok - my bad. I thought that you were talking about the stuff I just added like boyer_moore_search, etc. You meant the string routines.

So, in addition to

iterator_range<typename range_iterator<Range1T>::type>
find_first( Range1T& Input, const Range2T& Search);

you want something like:

const_iterator_range<typename const_range_iterator<Range1T>::type>
find_first( const Range1T& Input, const Range2T& Search);

Basically, when you pass in a constant range, you get back a constant range. is that correct?

anonymous — Wed, 14 Mar 2012 08:54:17 GMT

Yupp, I want to be able to write for example:

if( !find_first( foo.getName(), bar.getName() ).empty() ) { ... }