"Jonathan Turkanis" <technews@kangaroologic.com> wrote in message news:crl0i9$7mk$1@sea.gmane.org... | Jonathan Turkanis wrote: | | > 4. Thorsten asks why the widening and narrowing functions shouldn't be | > non-member functions. One answer is that code conversion can be | > (slightly) more efficient if a large buffer is used. Making the core | > conversion functions member functions allows buffers to be used for | > several string conversions. | | Hmmm ... This is true, but unfortunately doesn't apply to the version I posted. | | To take advantage of a large buffer, the input would have to be presented in a | manner that gives the implementaion access to underlying characters arrays. | (This would be the case if, e.g., the input were basic_strings, so that data() | could be used, or if there were a standard iterator category 'Contiguous | Traversal': http://tinyurl.com/4wynl.) | | I think the added flexibility of the overloads taking iterators is more | significant than the ability to buffer. I can't really figure out how this buffering should work. Buffering of what? I agree that there should be iterator versions underneith the range interface (that's how it all works.) Jonathan: | template<typename WideStr> | basic_string<typename Codecvt::extern_type> | narrow(const WideStr& str) | { | string_converter<> cvt; | return cvt::narrow(str); | } The could be specified as template< class NarrowString, class ReadableWideForwardRange, class Codecvt > NarrowString narrow( const ReadableWideForwardRange& r, const Codecvt& cc ); ... utf8_codecvt_facet<char_t> cc; wstring w1 = L"bar"; string s1 = std::narrow<string>( L"foo", cc ); string s2 = std::narrow<string>( make_iterator_range( w1, w1 + 2 ), cc ); vector<char> s3 = std::narrow<vector<char> >( w1, cc ); Beman: | > Preferable, the template parameter is just | >a ForwardRange FR with the requirement that a specialixation | >of std::char_traits exists for range_value<FR>::type. | |There are a lot of ways to redesign the interface. But if too many violent |changes are made we are no longer talking about existing practice and it |gets messy to try to convince the LWG. Anyone who wants to can propose an |alternative to the committee, but my guess is that it would have to be |dramatically better to have much chance. Well, we haven't talked about N1683 yet. :-) -Thorsten