which I would like to keep at the top of the file to make them easy to tweak if need be (especially in the case the variable is only used in one function, sure it may make sense to change it to a local variable, but that makes it more annoying to find to adjust). I think it ...
constexpr函数是能够在编译时期计算返回值的函数。如果函数的所有参数都是编译时常量,并且函数体内的计算...
int sz; // non-constexpr variable constexpr auto arraySize1 = sz; // error! not known at compilation std::array<int, sz> data1; // error! same problem constexpr auto arraySize2 = 10; // fine, 10 is a compile-time constant std::array<int, arraySize2> data2; // fine arraySi...
constexpr修饰函数时表示该函数的返回值有可能是const expression。后置const修饰的成员函数表示该函数隐含的...
/* We can see a FIELD_DECL in a pointer-to-member expression. */ case FIELD_DECL: case PARM_DECL: case USING_DECL: return true; case AGGR_INIT_EXPR: case CALL_EXPR: /* -- an invocation of a function other than a constexpr function ...
/* We can see a FIELD_DECL in a pointer-to-member expression. */ case FIELD_DECL: case PARM_DECL: case USING_DECL: return true; case AGGR_INIT_EXPR: case CALL_EXPR: /* -- an invocation of a function other than a constexpr function ...
It may contain local variable declarations, but the variable must be initialized. It must be a literal type, and can't bestaticor thread-local. The locally declared variable isn't required to beconst, and may mutate. Aconstexprnon-staticmember function isn't required to be implicitlyconst....
C++17 introduces the rule that static constexpr member variables are implicitly inline (P0386). Inline variables didn't exist before C++17. This means that in earlier C++ standards, a compiler may need a static constexpr member variable to be defined. If its address is taken, for example. ...
于是,constexpr修饰的是可以用于数组大小的。 而为什么在main的const是可以的呢?其实这跟const无关,而是使用了C99的一个特性,名叫variable length array(简称VLA),所以即使是这样: int main() { int i; cin >> i; int arr[i]; } 你使用你现在的GCC编译,也是可以通过的 ...
在C++ 中支持 全特化 (full specialization) 的模板很多,但是支持 偏特化 (partial specialization) 的模板并不多,事实上其实只有类模板 (class template) 和变量模板 (variable template) 两种支持,而变量模板其实可以看做类模板的语法糖,四舍五入一下其实只有类模板支持偏特化。不支持偏特化会导致有些代码十分难写...