c++ - Why is the template function ambiguous? -

when compile code error saying

call of overloaded swap(int&, int&) ambiguous

but i've written 1 swap function here.

can tell me why function ambiguous , changes need run program correctly?

using namespace std;  template <class t> void swap(t& x, t& y) {     t temp;     temp = x;     x = y;     y = temp; }  int main() {     int a, b;      cout << "enter 2 elements: ";      cin >> a;     cin >> b;      swap(a, b);     cout << "a "<<a << '\t'<<"b " << b << std::endl;      return 0; } 

why swapping function overloaded though has only swap function?

you should use

 ::swap(a,b); //use 1 in global namespace, 1 defined 

if call 1 defined. since std has defined swap function template, compiler search std namespace if not use ::.

more specifically, parameter a , b of type int, defined in std namespace, when compiler searches swap, find both versions: 1 in std namespace , other defined in global namespace. need tell compiler 1 should use explicitly, otherwise, lead ambiguity.