} constexpr int f5(int x) { // Error, function body contains more than if (x<0) // return statement. x = -x; return x; } 将函数模板声明为constexpr函数时,如果实例化导致函数不满足constexpr函数的需求,那么将忽略constexpr说明符。 例如: temp
countlower(s, n + 1, c + 1) : countlower(s, n + 1, c); } // output function that requires a compile-time constant, for testing template<int n> struct constN { constN() { std::cout << n << '\n'; } }; int main() { std::cout << "4! = "; constN<factorial(4)...
When a function template is declared as aconstexprfunction, if the instantiation results in a function that does not satisfy the requirements of aconstexprfunction, theconstexprspecifier is ignored. For example: template <class C> constexpr NL f6(C c) { // OK, the constexpr specifier ignore...
函数中仅包含一条 return 返回语句且函数的返回值类型不能是 void。When a constexpr function is call...
Within a constexpr or consteval function, we can use local variables that are not constexpr, and the value of these variables can be changed. As a silly example: #include<iostream>constevalintdoSomething(intx,inty)// function is consteval{x=x+2;// we can modify the value of non-const...
哪怕你写gcc -c a.c b.c,其实和gcc -c a.c && gcc -c b.c大体上是没区别的。在最后,所有的.o文件都被linker汇总link成一个大的可执行文件。2) static function。你可以把一个函数标记为static(也称为internal linkage),这样该函数的symbol就会被隐藏,从而该函数只存在在当前translation unit。换了下...
encrypted_string.cpp:17:13: note: ‘constexpr encrypted_string<std::integer_sequence<long unsigned int, _Idx ...> >::encrypted_string(const char*) [with long unsigned int ...I = {0ul, 1ul, 2ul, 3ul, 4ul}]’ is not usable as a constexpr function because: ...
看看这个:A constexpr function is not required to return a constant expression? 有用 回复 araraloren 3.5k2320 发布于 2016-03-16 更新于 2016-03-16 C++标准文档n45675.20小节讲的就是这个 int main() { int x = 0; int z = screen(x); //因为z是非constexpr的,不要求screen是constexpr的 cout...
constexpr.demo.cpp:3:15: warning: inline function ‘constexpr int bar()’ used but never defined [enabled by default] constexpr int bar(); ^ 可以看到,表示为constexpr的函数中可以使用函数的参数,并且可以使用其他为const类型的函数以及变量。
void function1() { x=100; // OK. } void function2() const { x=100; // ERROR. The const methods can't change the values of object fields. } }; 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. constexpr是一个不同的概念。如果将编译时常量作为参数传递,则它将一个函...