1// DR 339
2//
3// Test of the use of the ternary operator with SFINAE
4
5// Boilerplate helpers
6typedef char yes_type;
7struct no_type { char data[2]; };
8
9template<typename T> T create_a();
10template<typename T> struct type { };
11
12template<bool, typename T = void> struct enable_if { typedef T type; };
13template<typename T> struct enable_if<false, T> { };
14
15#define JOIN( X, Y ) DO_JOIN( X, Y )
16#define DO_JOIN( X, Y ) DO_JOIN2(X,Y)
17#define DO_JOIN2( X, Y ) X##Y
18
19template<typename T, typename U, typename V>
20typename enable_if<
21           (sizeof((create_a<T>()? create_a<U>() : create_a<V>()), 0) > 0),
22           yes_type>::type
23  check_ternary(int);
24
25template<typename T, typename U, typename V> no_type check_ternary(...);
26
27template<typename T, typename U, typename V>
28struct has_ternary
29{
30  static const bool value =
31    (sizeof(check_ternary<T, U, V>(0)) == sizeof(yes_type));
32};
33
34#ifdef __GXX_EXPERIMENTAL_CXX0X__
35#  define STATIC_ASSERT(Expr) static_assert(Expr, #Expr)
36#else
37#  define STATIC_ASSERT(Expr) int JOIN(a,__LINE__)[Expr? 1 : -1]
38#endif
39
40struct X { };
41struct Y { operator bool(); };
42
43STATIC_ASSERT((has_ternary<int, float, double>::value));
44STATIC_ASSERT((has_ternary<bool, double, double>::value));
45STATIC_ASSERT((!has_ternary<int, float*, double>::value));
46STATIC_ASSERT((!has_ternary<X, double, double>::value));
47STATIC_ASSERT((has_ternary<Y, double, double>::value));
48