C++ named requirements: LegacyIterator - cppreference.com (original) (raw)

The LegacyIterator 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, and LegacyRandomAccessIterator. 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 tables and concept definitions(since C++20) for the iterators do not specify complexity.

[edit] Requirements

The type It satisfies LegacyIterator if

• The type It satisfies CopyConstructible, and
• The type It satisfies CopyAssignable, and
• The type It satisfies Destructible, and
• The type It satisfies Swappable, and
• std::iterator_traits<It> has member typedefs: value_type,(until C++20) difference_type, reference, pointer, and iterator_category, and
• Given r, an lvalue of type It, 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 new iterator concepts introduced with C++20.

1. ↑ LegacyContiguousIterator category was only formally specified in C++17, but the iterators of std::vector, std::basic_string, std::array, and std::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