Difference between revisions of "cpp/iterator/input or output iterator"
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(mention how to make a class satisfy this concept) |
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The exposition-only concept {{c|/*can-reference*/}} is satisfied if and only if the type is referenceable (in particular, not {{c|void}}). | The exposition-only concept {{c|/*can-reference*/}} is satisfied if and only if the type is referenceable (in particular, not {{c|void}}). | ||
| − | {{cpp/concepts/equality preservation}} | + | {{todo|Is *i required to be equality-preserving?}} |
| + | <!-- {{cpp/concepts/equality preservation}} --> | ||
| + | |||
| + | ===Notes=== | ||
| + | A typical {{tt|input_or_output_iterator}} class only needs to be {{lconcept|movable}}, and provide the following members: | ||
| + | |||
| + | * Member typedef {{tt|difference_type}} (used by {{lc|std::iter_difference_t}}). | ||
| + | * Prefix {{tt|operator++}} that returns a reference to {{tt|*this}}. | ||
| + | * Postfix {{tt|operator++}}. | ||
| + | * The dereference operator {{tt|operator*}}. | ||
| + | |||
| + | Alternatively, the {{tt|difference_type}} can be provided by specializing either {{lc|std::iterator_traits}} or {{lc|std::incrementable_traits}}. The functions can be defined as non-members, to be found by [[cpp/language/adl|argument-dependent lookup]]. | ||
| − | |||
{{tt|input_or_output_iterator}} itself only specifies operations for dereferencing and incrementing an iterator. Most algorithms will require additional operations, for example: | {{tt|input_or_output_iterator}} itself only specifies operations for dereferencing and incrementing an iterator. Most algorithms will require additional operations, for example: | ||
* comparing iterators with sentinels (see {{lconcept|sentinel_for}}); | * comparing iterators with sentinels (see {{lconcept|sentinel_for}}); | ||
| − | * reading values from an iterator (see {{lconcept|indirectly_readable}} and {{lconcept|input_iterator}}) | + | * reading values from an iterator (see {{lconcept|indirectly_readable}} and {{lconcept|input_iterator}}); |
| − | * writing values to an iterator (see {{lconcept|indirectly_writable}} and {{lconcept|output_iterator}}) | + | * writing values to an iterator (see {{lconcept|indirectly_writable}} and {{lconcept|output_iterator}}); |
| − | * a richer set of iterator movements (see {{lconcept|forward_iterator}}, {{lconcept|bidirectional_iterator}}, {{lconcept|random_access_iterator}}) | + | * a richer set of iterator movements (see {{lconcept|forward_iterator}}, {{lconcept|bidirectional_iterator}}, {{lconcept|random_access_iterator}}). |
Unlike the {{named req|Iterator}} requirements, the {{tt|input_or_output_iterator}} concept does not require copyability. | Unlike the {{named req|Iterator}} requirements, the {{tt|input_or_output_iterator}} concept does not require copyability. | ||
{{langlinks|es|ja|zh}} | {{langlinks|es|ja|zh}} | ||
Revision as of 21:57, 7 September 2023
| Defined in header <iterator>
|
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| template <class I> concept input_or_output_iterator = |
(since C++20) | |
The input_or_output_iterator concept forms the basis of the iterator concept taxonomy; every iterator type satisfies the input_or_output_iterator requirements.
The exposition-only concept /*can-reference*/ is satisfied if and only if the type is referenceable (in particular, not void).
| This section is incomplete Reason: Is *i required to be equality-preserving? |
Notes
A typical input_or_output_iterator class only needs to be movable, and provide the following members:
- Member typedef
difference_type(used by std::iter_difference_t). - Prefix
operator++that returns a reference to*this. - Postfix
operator++. - The dereference operator
operator*.
Alternatively, the difference_type can be provided by specializing either std::iterator_traits or std::incrementable_traits. The functions can be defined as non-members, to be found by argument-dependent lookup.
input_or_output_iterator itself only specifies operations for dereferencing and incrementing an iterator. Most algorithms will require additional operations, for example:
- comparing iterators with sentinels (see
sentinel_for); - reading values from an iterator (see
indirectly_readableandinput_iterator); - writing values to an iterator (see
indirectly_writableandoutput_iterator); - a richer set of iterator movements (see
forward_iterator,bidirectional_iterator,random_access_iterator).
Unlike the LegacyIterator requirements, the input_or_output_iterator concept does not require copyability.
