I want to do structure with some type and with ability to use another comparator somewhen.This way of do template is not work.How I can do it correct?
template<typename T, typename Comparator = std::less<T>> struct list_heap{}; bool min(int &a, int &b){return a<b;}; int main(){list_heap<int>r;list_heap<int, min>rr;return 0;}; min is a name of a function, not a type. The type of min is bool(*)(int&, int&).
You can initialize your struct by giving the full type name:
list_heap<int, bool(*)(int&, int&)> rr; //or something that bool(*)(int&, int&) will be convertible to: list_heap<int, std::function<bool(int&, int&)>> rr; Or by utilizing decltype to let compiler deduce the type:
list_heap<int, decltype(min)> rr; If you cannot edit main, the only other option is to change min into function object:
struct min { bool operator()(int &a, int &b){return a<b;}; }; Make sure you don't have using namespace std; in your code or std::min might collide with your own min.
min into function object, let me add that to the answer.