Dave Abrahams wrote:
on Thu Oct 06 2011, lcaminiti <lorcaminiti-AT-gmail.com> wrote:
Dave Abrahams wrote:
I don't think you can evaluate these choices just by looking at the implementations. Before anyone else votes option 1, I'd like to see
Well, I'm not so sure I like option 1 anymore... if option 1 was an oversight in STL then there is no sense in perpetuating the specification error in Boost.Algorithm (perhaps Boost.Algorithm should then go with option 2 and explain the rationale of why it's different than what STL does for example with std::find).
somebody write the description of the algorithm, including the concept requirements. With option 2, we know that == has to be an equivalence relation. The semantics in option 1 are a lot fuzzier.
Good point! I'll try to start :)
template< typename Iter, typename Val > requires InputIterator<Iter>, EqualityComparable<iterator_traits<Iter>::value_type, Val> bool none_of_equal ( Iter first, Iter last, Val const& val ) ; // option 1a
What you failed to do here was to describe the semantic requirements on EqualityComparable<A,B>, where A != B.
I see, how about the semantic of EqualityComparable<A, B> with A != B is up for discussion :) Here's a (funny) way I could satisfy the EqualityComparable<A, B> requirement: #include <vector> #include <algorithm> struct orange { int weight; }; struct apple { int weight; }; bool operator== ( orange const& l, apple const& r ) { return l.weight == r.weight; } // comparing apples with oranges?! int main ( ) { std::vector<orange> v(2); std::find(v.begin(), v.end(), apple()); return 0; } No type conversion, EqualityComparable<A, B> is some sort of equivalence that can be defined among the different types without converting them into one another... isn't that confusing :) I am starting to find option 1 confusing... (like the example above). Maybe is best to go with option 2 for the _equal functions requiring the types to be the same because that's the commonly understood semantic of ==. For comparing apples with oranges (and other strange things), we can use the predicate version of the algorithms. --Lorenzo -- View this message in context: http://boost.2283326.n4.nabble.com/Boost-Algorithm-design-question-tp3876424... Sent from the Boost - Dev mailing list archive at Nabble.com.