but it need not necessarily do so. In a context that requires a compile-time value (e.g., an array length or a nontype template argument), the compiler will attempt to evaluate a call to a constexpr function at compile time and issue an error if that is not possible (since a consta...
but it need not necessarily do so. In a context that requires a compile-time value (e.g., an array length or a nontype template argument), the compiler will attempt to evaluate a call to a constexpr function at compile time and issue an error if that is not possible (since a consta...
constexpr int *np = nullptr; // np is a constant pointer to int that is null int j = 0; constexpr int i = 42; // type of i is const int // i and j must be defined outside any function <==i和j必须定义在任何函数体之外 constexpr const int *p = &i; // p is a constant...
{returnN; }// Recursive constexpr functionconstexprintfac(intn){returnn ==1?1: n * fac(n -1); }// User-defined typeclassFoo{public:constexprexplicitFoo(inti): _i(i){}constexprintGetValue()const{return_i; }private:int_i; };intmain(){// foo is const:constexprFoofoo(5);//...
exp2(x * x, n / 2) : exp2(x * x, (n - 1) / 2) * x; } // Compile-time computation of array length template<typename T, int N> constexpr int length(const T(&)[N]) { return N; } // Recursive constexpr function constexpr int fac(int n) { return n == 1 ? 1 :...
}// Recursive constexpr functionconstexprintfac(intn){returnn ==1?1: n *fac(n -1); }// User-defined typeclassFoo{public:constexprexplicitFoo(inti): _i(i) {}constexprintGetValue()const{return_i; }private:int_i; };intmain(){// foo is const:constexprFoofoo(5);// foo = Foo...
expression must have a constant value -- constexpr function function "Type::impl_size" (declared at line 70) is not defined 第70行是在报头上定义impl_size。 MCVE: #include <cstddef> template <typename T1, std::size_t N1, std::size_t N2> struct Pimpl; class Type { private: static...
// Recursive constexpr function constexpr int fac(int n) { return n == 1 ? 1 : n*fac(n - 1); } // User-defined type class Foo { public: constexpr explicit Foo(int i) : _i(i) {} constexpr int GetValue() { return _i; ...
constexpr extern int j; // Error, not a definition constexpr int f1(); // OK, function declaration, but must be defined before use 如果您声明的函数不是具有constexpr说明符的构造函数,那么该函数是constexpr函数。 同样,如果使用constexpr说明符声明构造函数,那么该构造函数是constexpr构造函数。constex...
In the Visual Studio debugger, when debugging a non-optimised Debug build, you can tell whether a constexpr function is being evaluated at compile time by putting a breakpoint inside it. If the breakpoint is hit, the function was called at run-time. If not, then the function was called...