Re: [Boost-users] Re: copy_if

On Sat, 2003-09-13 at 20:52, Witz wrote:

You can find an implementation of copy_if in Boost Wiki here:

http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?STLAlgorithmE...

An extension that i find useful is the following:

template std::pair copy_if(II ibegin, II iend, OI obegin, OI oend, PRED p) { for(; ibegin != iend; ++ibegin) { if(p(*ibegin)) { *obegin = *ibegin; if(++obegin == oend) break; } } return std::make_pair(ibegin, obegin); }

Here we have a finite sized sink. Items are copied from the source if they satisfy the condition and if there is room left in the sink. The positions reached are returned on termination of the algorithm.

Witz

That's very useful. I've been wondering about that - backinserter is fine if you really do want to append, but I'd never before seen mention of a solution for limiting based on size of output. I guess a final option would be "copy into, then append if full". Although if you don't fill the container, then presumably there are some elements still at the end - I can't imagine wanting this. What would make more sense is "truncate container and then append" - which is probably better done outside the algorithm, yes? Thanks heaps - particularly that link is excellent, Zenaan