cpp/ranges/view counted

A counted view presents a of the elements of the counted range  for some iterator  and non-negative integer.

A counted range is the  elements starting with the element pointed to by  and up to but not including the element, if any, pointed to by the result of  applications of.

If, the counted range is valid and empty. Otherwise, the counted range is only valid if is positive,  is dereferenceable, and  is a valid counted range.

Formally, if and  are expressions,  is, and  is , then
 * if models  and  models ,
 * if models, then  is expression-equivalent to ,
 * otherwise, if models, then  is expression-equivalent to ,
 * otherwise, is expression-equivalent to.
 * Otherwise, is ill-formed.