24 Iterators library [iterators]

The Cpp17Iterator requirements form the basis of the iterator taxonomy; every iterator meets the Cpp17Iterator requirements.

This set of requirements specifies operations for dereferencing and incrementing an iterator.

Most algorithms will require additional operations to read ([input.iterators]) or write ([output.iterators]) values, or to provide a richer set of iterator movements ([forward.iterators], [bidirectional.iterators], [random.access.iterators]).

A type X meets the Cpp17Iterator requirements if

• (2.1)
  X meets the Cpp17CopyConstructible, Cpp17CopyAssignable, Cpp17Swappable, and Cpp17Destructible requirements ([utility.arg.requirements], [swappable.requirements]), and
• (2.2)
  iterator_traits<X>​::​difference_type is a signed integer type or void, and
• (2.3)
  the expressions in Table 73 are valid and have the indicated semantics.