C++关键字 constexpr c++程序中的某些词具有某些特殊的含义,这些词被称为关键字-keyword。 为什么需要constexpr关键字? constexpr variables constexpr andconstant expressions constexpr and Pointers constexpr functions constexpr constructors constexpr destructor(C++起,先不考虑) ---接下来进行一一介绍: constant ...
/* -- an invocation of a function other than a constexpr function or a constexpr constructor. */ { tree fun = get_function_named_in_call (t); const int nargs = call_expr_nargs (t); i = 0; if (is_overloaded_fn (fun)) { if (TREE_CODE (fun) == FUNCTION_DECL) { if (buil...
/* -- an invocation of a function other than a constexpr function or a constexpr constructor. */ { tree fun = get_function_named_in_call (t); const int nargs = call_expr_nargs (t); i = 0; if (is_overloaded_fn (fun)) { if (TREE_CODE (fun) == FUNCTION_DECL) { if (buil...
"no support constructor"); return t2; } template <typename T1, typename T2, typename ... Args> const T1& select_constructor(const T2& t2, Args ... args) { if constexpr(std::is_same<T1, T2>::value) { return t2; } else { return select_constructor<T1,Args...>(args...); } ...
// uses a non-constexpr constructor. constexpr void f4(int x) { // Error, return type should not be void. return; } constexpr int f5(int x) { // Error, function body contains more than if (x<0) // return statement. x = -x; ...
constexpr test3 x(100); // OK. Constructor is constexpr. int array[x.getvalue()]; // OK. x.getvalue() is constexpr and can be evaluated at compile time. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. ...
Constructor is constexpr. int array[x.getvalue()]; // OK. x.getvalue() is constexpr and can be evaluated at compile time. 4.建议 Tips from the book Effective Modern C++ by Scott Meyers about constexpr: constexpr 对象是const,在编译期间使用已知的值初始化; constexpr 函数当使用在编译期间...
struct S { constexpr S(int i) : mem(i) { } // OK, declaration of a constexpr constructor private: int mem; }; constexpr S s(55); // OK, invocation of a constexpr constructor 関数または関数テンプレートのいずれかの宣言が constexpr を使用して指定されている場合、そのすべての...
{ ^ /usr/bin/../lib/gcc/aarch64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/functional:1834:11: note: 'function<double (double)>' is not literal because it is not an aggregate and has no constexpr constructors other than copy or move constructors class function<_Res(_Arg...
·a trivial default constructor or at least one constexpr constructor other than the copy constructor, all non-static data members and base classes of literal types; or an array of literal type. 大意是: 一个字面值类型应具有如下特点 是一个标量类型(如整型、浮点型、物理类型和枚举类型) 或是一...