[range.as.const.overview] (original) (raw)

25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.22 As const view [range.as.const]

25.7.22.1 Overview [range.as.const.overview]

as_const_view presents a view of an underlying sequence as constant.

That is, the elements of an as_const_view cannot be modified.

Let E be an expression, let T be decltype((E)), and let U be remove_cvref_t<T>.

The expression views​::​as_const(E) is expression-equivalent to:

• Otherwise, if U denotes empty_view<X>for some type X, then auto(views​::​empty<const X>).
• Otherwise, if U denotes span<X, Extent>for some type X and some extent Extent, then span<const X, Extent>(E).
• Otherwise, if U denotes ref_view<X> for some type X andconst X models constant_range, then ref_view(static_cast<const X&>(E.base())).
• Otherwise, if E is an lvalue,const U models constant_range, andU does not model view, then ref_view(static_cast<const U&>(E)).
• Otherwise, as_const_view(E).

[Example 1: template<constant_range R> void cant_touch_this(R&&); vector<char> hammer = {'m', 'c'}; span<char> beat = hammer; cant_touch_this(views::as_const(beat)); — _end example_]