1 // DR 339
2 //
3 // Test of the use of the function call operator with SFINAE
4 typedef char yes_type;
5 struct no_type { char data[2]; };
6 
7 template<typename T> T create_a();
8 
9 template<typename T> struct type { };
10 
11 template<bool, typename T = void> struct enable_if { typedef T type; };
12 template<typename T> struct enable_if<false, T> { };
13 
14 template<typename F, typename T1, typename T2>
15   typename enable_if<sizeof(create_a<F>()(create_a<T1>(), create_a<T2>()), 1),
16 		     yes_type>::type
17   check_is_callable2(type<F>, type<T1>, type<T2>);
18 
19 no_type check_is_callable2(...);
20 
21 template<typename F, typename T1, typename T2 = T1>
22 struct is_callable2
23 {
24   static const bool value =
25     (sizeof(check_is_callable2(type<F>(), type<T1>(), type<T2>()))
26      == sizeof(yes_type));
27 };
28 
29 #define JOIN( X, Y ) DO_JOIN( X, Y )
30 #define DO_JOIN( X, Y ) DO_JOIN2(X,Y)
31 #define DO_JOIN2( X, Y ) X##Y
32 
33 #ifdef __GXX_EXPERIMENTAL_CXX0X__
34 #  define STATIC_ASSERT(Expr) static_assert(Expr, #Expr)
35 #else
36 #  define STATIC_ASSERT(Expr) int JOIN(a,__LINE__)[Expr? 1 : -1]
37 #endif
38 
39 
40 struct A;
41 struct B;
42 
43 struct A {
44   A(B);
45 };
46 
47 struct B {
48   B(A);
49 };
50 
51 struct F1 { };
52 
53 struct F2 {
54   bool operator()(int, float);
55 };
56 
57 struct F3 {
58   bool operator()(int);
59 };
60 
61 struct F4 {
62   void operator()(A, A);
63   void operator()(B, B);
64 };
65 
66 struct F5 {
67   void operator()(A, A);
68 
69 private:
70   void operator()(B, B);
71 };
72 
73 STATIC_ASSERT((is_callable2<int(*)(int, int), long, int>::value));
74 STATIC_ASSERT((!is_callable2<int(*)(int, int), int*, int>::value));
75 STATIC_ASSERT((!is_callable2<F1, int, int>::value));
76 STATIC_ASSERT((is_callable2<F2, int, int>::value));
77 STATIC_ASSERT((!is_callable2<F2, int*, int>::value));
78 STATIC_ASSERT((!is_callable2<F3, int, int>::value));
79 STATIC_ASSERT((is_callable2<F4, A, A>::value));
80 STATIC_ASSERT((is_callable2<F4, B, B>::value));
81 STATIC_ASSERT((!is_callable2<F4, A, B>::value));
82 STATIC_ASSERT((is_callable2<F5, A, A>::value));
83 STATIC_ASSERT((!is_callable2<F5, A, B>::value));
84