TheLegacyIterator requirements describe types that can be used to identify and traverse the elements of a container.

LegacyIterator is the base set of requirements used by other iterator types:LegacyInputIterator,LegacyOutputIterator,LegacyForwardIterator,LegacyBidirectionalIterator, andLegacyRandomAccessIterator. Iterators can be thought of as an abstraction of pointers.

All the categories of iterators require only those functions that are realizable for a given category in constant time (amortized). Therefore, requirement tablesand concept definitions(since C++20) for the iterators do not specify complexity.

[edit]Requirements

The typeIt satisfiesLegacyIterator if

• The typeIt satisfiesCopyConstructible, and
• The typeIt satisfiesCopyAssignable, and
• The typeIt satisfiesDestructible, and
• The typeIt satisfiesSwappable, and
• std::iterator_traits<It> has member typedefs:value_type,(until C++20)difference_type,reference,pointer, anditerator_category, and
• Givenr, an lvalue of typeIt, the following expressions must be valid and have their specified effects:

[edit]Notes

Note on terminology: The following table shows the names used on this site and corresponding C++ Standard names (with the same meaning).The "Legacy" (and “Cpp17”) prefix emphasizes compatibility with pre-C++20 standards and is used to distinguish these requirements from the newiterator concepts introduced with C++20.

1. ↑LegacyContiguousIterator category was only formally specified in C++17, but the iterators ofstd::vector,std::basic_string,std::array, andstd::valarray, as well as pointers into C arrays are often treated as a separate category in pre-C++17 code.

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit]See also

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