This sub-clause contains templates that may be used to query properties of types at compile time.
| Template | Value |
|
template <class T> struct alignment_of; |
alignof(T). Requires: alignof(T) shall be a valid expression ([expr.alignof]) |
| template <class T> struct rank; | If T names an array type, an integer value representing the number of dimensions of T; otherwise, 0. |
| template <class T, unsigned I = 0> struct extent; | If T is not an array type, or if it has rank less than or equal to I, or if I is 0 and T has type “array of unknown bound of U”, then 0; otherwise, the bound ([dcl.array]) of the I'th dimension of T, where indexing of I is zero-based |
[ Example:
// the following assertions hold:
assert(rank<int>::value == 0);
assert(rank<int[2]>::value == 1);
assert(rank<int[][4]>::value == 2);
— end example ]
[ Example:
// the following assertions hold:
assert(extent<int>::value == 0);
assert(extent<int[2]>::value == 2);
assert(extent<int[2][4]>::value == 2);
assert(extent<int[][4]>::value == 0);
assert((extent<int, 1>::value) == 0);
assert((extent<int[2], 1>::value) == 0);
assert((extent<int[2][4], 1>::value) == 4);
assert((extent<int[][4], 1>::value) == 4);
— end example ]