< cpp‎ | experimental‎ | ranges
Technical specifications
Filesystem library (filesystem TS)
Library fundamentals (library fundamentals TS)
Library fundamentals 2 (library fundamentals 2 TS)
Extensions for parallelism (parallelism TS)
Extensions for concurrency (concurrency TS)
Concepts (concepts TS)
Ranges (ranges TS)
Special mathematical functions (special math TR)
Iterators library
Iterator concepts
Indirect callable concepts
Common algorithm requirements
Concept utilities
Iterator utilities and operations
Iterator traits
Iterator adaptors
Stream iterators
template <class I>

concept bool Iterator =
  requires(I i) {
    { *i } -> auto&&; // Requires: i is dereferenceable
  } &&

(ranges TS)

The Iterator concept forms the basis of the iterator concept taxonomy; every iterator satisfies the Iterator requirements.

[edit] Equality preservation

An expression is equality preserving if it results in equal outputs given equal inputs.

  • The inputs to an expression consist of its operands.
  • The outputs of an expression consist of its result and all operands modified by the expression (if any).

Every expression required to be equality preserving is further required to be stable: two evaluations of such an expression with the same input objects must have equal outputs absent any explicit intervening modification of those input objects.

Unless noted otherwise, every expression used in a requires-expression is required to be equality preserving and stable, and the evaluation of the expression may only modify its non-constant operands. Operands that are constant must not be modified.

[edit] Notes

Iterator itself only specifies operations for dereferencing and incrementing an iterator. Most algorithms will require additional operations, for example:

The -> auto&& constraint implies that the result type of the deference cannot be void.