编译期算结果C98示例：
1 2 3 4 5 6 7 | template <int n> struct fact98 { static const int value = n * fact98<n - 1>::value; }; template <> struct fact98<0> { static const int value = 1; }; std::cout << fact98<5>::value << std::endl; |
或C11的示例：
1 2 3 | constexpr int fact11(int n) { return n <= 1 ? 1 : (n * fact11(n - 1)); } |
C11中不能使用变量和循环，C14中可以：
1 2 3 4 5 | constexpr int fact14(int n) { int s = 1; for (int i = 1; i <= n; i++) { s = s * i; } return s; } |
编译期检查1：
1 2 3 4 5 6 7 | static_assert(sizeof(void *) == 8, "expected 64-bit platform"); template<typename T, int Row, int Column> struct Matrix { static_assert(Row >= 0, "Row number must be positive."); static_assert(Column >= 0, "Column number must be positive."); }; |
编译期检查2：
1 2 3 4 5 6 7 8 9 | struct A { void foo(){} int member; }; template<typename Function> std::enable_if_t<!std::is_member_function_pointer_v<Function>> foo(Function&& f) { } foo([] {}); //ok foo(&A::foo); //compile error: no matching function for call to 'foo(void (A::*)())' |
编译期检查3：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | template< class, class = void > struct has_foo : std::false_type {}; template< class T > struct has_foo< T, std::void_t<decltype(std::declval<T>().foo())> > : std::true_type {}; template< class, class = void > struct has_member : std::false_type {}; template< class T > struct has_member< T, std::void_t<decltype(std::declval<T>().member)> > : std::true_type {}; struct A { void foo(){} int member; }; static_assert(has_foo< A >::value); static_assert(has_member< A >::value); |