26 Ranges library [ranges]

26.4 Range requirements [range.req]

26.4.1 General [range.req.general]

Ranges are an abstraction that allows a C++ program to operate on elements of data structures uniformly.
Calling ranges​::​begin on a range returns an object whose type models input_or_output_iterator ([iterator.concept.iterator]).
Calling ranges​::​end on a range returns an object whose type S, together with the type I of the object returned by ranges​::​begin, models sentinel_for<S, I>.
The library formalizes the interfaces, semantics, and complexity of ranges to enable algorithms and range adaptors that work efficiently on different types of sequences.
The range concept requires that ranges​::​begin and ranges​::​end return an iterator and a sentinel, respectively.
The sized_range concept refines range with the requirement that ranges​::​size be amortized .
The view concept specifies requirements on a range type to provide operations with predictable complexity.
Several refinements of range group requirements that arise frequently in concepts and algorithms.
Common ranges are ranges for which ranges​::​begin and ranges​::​end return objects of the same type.
Random access ranges are ranges for which ranges​::​begin returns a type that models random_access_iterator ([iterator.concept.random.access]).
(Contiguous, bidirectional, forward, input, and output ranges are defined similarly.)
Viewable ranges can be converted to views.