Template parameters in C++ templates
I am trying to use template template parameters, similar to what is done here and here (and many other places).
#include
template
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There is another thing you can do instead of modifying the function definition, i.e. use template alias to adapt
std::vector:#include <vector> #include<iostream> template< template<class> class A, class B > void f(A<B> &value) { for( auto & x : value ) { std::cout << x << std::endl; } } template< class T > using VectorAdapter = std::vector<T>; int main() { VectorAdapter<int> value {1, 2, 3}; f(value); }讨论(0) -
Vector has 2 template parameters, (the second one is almost never used and has a default allocator type)
template < class T, class Alloc = allocator<T> > class vector;So it should be:
template<template<class,class> class H, class S,class A> void f(const H<S,A> &value) { }讨论(0) -
Pretty sure this is what you're looking for:
template<template<class, class...> class V, class T, class... Args> void fn(V<T,Args...>& value) { // use value here. }Invoked simply as:
std::vector<int> v; fn(v);And before you ask, yes, you can do it with templates that need more parameters (like
std::map<>, etc), Just make sureArg...covers the optionals and you specify the mandatory ones you care about. Such as:#include <iostream> #include <vector> #include <list> #include <map> #include <unordered_map> #include <cstdlib> template< template<class, class...> class V, class T, class... Args> void fn_seq(const V<T,Args...>& value) { std::cout << __PRETTY_FUNCTION__ << '\n'; // use value here. } template< template<class, class, class...> class C, class K, class V, class... Args> void fn_assoc(const C<K,V,Args...>& value) { // use value here. std::cout << __PRETTY_FUNCTION__ << '\n'; } int main() { std::vector<int> vec; fn_seq(vec); std::list<double> lst; fn_seq(lst); std::map<int, float> m; fn_assoc(m); std::unordered_map<long, long> um; fn_assoc(um); return EXIT_SUCCESS; }Output
void fn_seq(const V<T, Args...> &) [V = vector, T = int, Args = <std::__1::allocator<int>>] void fn_seq(const V<T, Args...> &) [V = list, T = double, Args = <std::__1::allocator<double>>] void fn_assoc(const C<K, V, Args...> &) [C = map, K = int, V = float, Args = <std::__1::less<int>, std::__1::allocator<std::__1::pair<const int, float> >>] void fn_assoc(const C<K, V, Args...> &) [C = unordered_map, K = long, V = long, Args = <std::__1::hash<long>, std::__1::equal_to<long>, std::__1::allocator<std::__1::pair<const long, long> >>]讨论(0)
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