[iterator.concept.inc] (original) (raw)

23 Iterators library [iterators]

23.3 Iterator requirements [iterator.requirements]

23.3.4 Iterator concepts [iterator.concepts]

23.3.4.5 Concept incrementable [iterator.concept.inc]

The incrementable concept specifies requirements on types that can be incremented with the pre- and post-increment operators.

The increment operations are required to be equality-preserving, and the type is required to be equality_­comparable.

[ Note

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This supersedes the annotations on the increment expressions in the definition of weakly_­incrementable.

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template concept incrementable = regular && weakly_incrementable && requires(I i) { { i++ } -> same_as; };

Let a and b be incrementable objects of type I.

I models incrementable only if

• If bool(a == b) then bool(a++ == b).
• If bool(a == b) then bool(((void)a++, a) == ++b).

[ Note

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The requirement thata equals bimplies++a equals ++b(which is not true for weakly incrementable types) allows the use of multi-pass one-directional algorithms with types that model incrementable.

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