Hi, On Sun, Mar 13, 2005 at 10:04:05PM -0800, Eric Niebler wrote:
Background:
I have been working on range-based algorithms and adaptors. The algorithms are variants of the std::algorithms that accept ranges instead of a [begin,end) iterator pair. The adaptors are like the iterator adaptors, except they adapt ranges.
Following the principal of least surprise, I want to call my range adaptors filter_range, indirect_range, reverse_range and transform_range (to parallel filter_iterator, indirect_iterator, etc). But I can't do this, because there already is a transform_range, and it's a function!
Problem:
At the bottom of iterator_range.hpp is this:
template< typename SeqT, typename Range, typename FuncT > inline SeqT transform_range( const Range& r, FuncT Func ) { SeqT Seq; std::transform( begin( r ), end( r ), std::back_inserter(Seq), Func ); return Seq; }
I'm not sure why. It looks like a range-based algorithm, but ... why provide only one? (Two actually -- copy_range is there also.) And why call it transform_range() instead of just calling it "transform" and making it part of a complete range-based algorithm library?
Solution:
I suggest the functions copy_range() and transform_range() should be removed or moved into a "deprecated" namespace, freeing up the identifier "boost::transform_range" to be a type, analagous to boost::transform_iterator. Development should proceed on a range-based algorithms library to fill the need that the existing "transform_range()" function is meeting.
Thoughts?
Originaly I was the author of iterator_range class and the utilities. It was then taken to Boost.Range library as a more meaningful place. Rantionale for these two functions was to improve the usability of iterator_range class. transform_range is not so crucial, but the copy_range is very important. Without it you cannot easily convert iterator_range to a string for instance. You need to go through iterator-constructor. So instead of str=copy_range<std::string>(aRange); You need to write str=std::string(aRange.begin(), aRange.end()); The second one is not as nice, but what is more important, it disallows you to pass a range by value in a chain. In other words, you cannot write str=copy_range<std::string>(find_first(input,"helo")); To sumarize, copy_range is an essential utility, that provides a way of copying between different range types, especialy the legacy ones like std::string. Therefor it has an important place in the Boost.Range library. Regards, Pavol