David Abrahams wrote:
Careful; vector iterators are not neccessarily pointers.
Hm yes, that's true. But does this matter? I have a vector of some type, and a vector of pointers to some type. I don't even deal with iterators when working on the pointer-vector.
struct indirect_less { template <class It> bool operator()(It i1, It i2) const { typedef typename std::iterator_traits<It>::value_type value_type; return std::less<value_type>()(i1,i2); } };
sort(ptrcoll.begin(), ptrcoll.end, indirect_less());
Ah I see. But what, if I want to abstract from the predicate? I want to create a class which is as generic as possible, so I don't have to rewrite it for each and every possible predicate. What if I want to pass the predicate to the constructor of this template. For one, passing a pointer to a function returning bool and taking on argument must be possible, and also passing a function object, maybe of type std::unary_function. template<typename It> class indirect { const std::unary_function<It,bool>& fctor_; public: indirect( const std::unary_function<It,bool>& fctor ): fctor_(fctor) {} bool operator()(It i1, It i2) const { typedef typename std::iterator_traits<It>::value_type value_type; return fctor_<It,bool>()(i1,i2); } }; Would that work? -- Matthias Kaeppler