On 20.02.2013, at 19:55, Marshall Clow wrote:
I'm proposing to change the interface to:
template<typename InputIterator, typename OutputIterator, typename Predicate> std::pair<InputIterator, OutputIterator> copy_while ( InputIterator first, InputIterator last, OutputIterator result, Predicate p );
i.e, changing the return type to return both iterators.
What this means: * If you're not calling copy_while (or copy_until), then this change won't affect you. * If you're not using the return value, then this change won't affect you. * If you are using the return value, then you will have to change your code thus: Old foo = copy_while ( first, last, out, p ); New: foo = copy_while ( first, last, out, p ).second;
If you want to ease transition, I once wrote a biased_pair type, which is basically a pair with an implicit conversion to one of its member types. template <typename T1, typename T2> struct right_biased_pair { // consider deriving from std::pair instead of aping it T1 first; T2 second; // constructors and stuff operator std::pair<T1, T2>() { return std::pair<T1, T2>(first, second); } // the bias operator T2() const { return second; } }; Then you can make copy_while return a right_biased_pair<InputIterator, OutputIterator> and code of the form out = copy_while(first, last, out, p); will keep working. No idea if that's worth it to you, just saying that the option is there. Sebastian