1 // { dg-do run { target c++11 } }
2 // A basic implementation of TR1's mem_fn using variadic teplates
3 // Contributed by Douglas Gregor <doug.gregor@gmail.com>
4 #include <cassert>
5
6 template<typename R, typename Class, typename... Args>
7 class Mem_fn
8 {
9 public:
Mem_fn(R (Class::* pmf)(Args...))10 explicit Mem_fn(R (Class::*pmf)(Args...)) : pmf(pmf) { }
11
operator()12 R operator()(Class& object, Args... args)
13 {
14 return (object.*pmf)(args...);
15 }
16
operator()17 R operator()(Class* object, Args... args)
18 {
19 return (object->*pmf)(args...);
20 }
21
22 R (Class::*pmf)(Args...);
23 };
24
25 template<typename R, typename Class, typename... Args>
26 inline Mem_fn<R, Class, Args...>
mem_fn(R (Class::* pmf)(Args...))27 mem_fn(R (Class::* pmf)(Args...))
28 {
29 return Mem_fn<R, Class, Args...>(pmf);
30 }
31
32 class X {
33 public:
negate(int x)34 int negate(int x) { return -x; }
plus(int x,int y)35 int plus(int x, int y) { return x + y; }
36 };
37
main()38 int main()
39 {
40 X x;
41 X* xp = &x;
42
43 assert(mem_fn(&X::negate)(x, 17) == -17);
44 assert(mem_fn(&X::negate)(xp, 17) == -17);
45 assert(mem_fn(&X::plus)(x, 17, 25) == 42);
46 assert(mem_fn(&X::plus)(xp, 17, 25) == 42);
47
48 return 0;
49 }
50