Interoperable Iterator Concept

.. Copyright David Abrahams 2006. Distributed under the Boost .. Software License, Version 1.0. (See accompanying .. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

Interoperable Iterator Concept ..............................

A class or built-in type X that models Single Pass Iterator is interoperable with a class or built-in type Y that also models Single Pass Iterator if the following expressions are valid and respect the stated semantics. In the tables below, x is an object of type X, y is an object of type Y, Distance is iterator_traits<Y>::difference_type, and n represents a constant object of type Distance.

+-----------+-----------------------+---------------------------------------------------+ |Expression |Return Type |Assertion/Precondition/Postcondition | +===========+=======================+===================================================+ |y = x |Y |post: y == x | +-----------+-----------------------+---------------------------------------------------+ |Y(x) |Y |post: Y(x) == x | +-----------+-----------------------+---------------------------------------------------+ |x == y |convertible to bool|== is an equivalence relation over its domain. | +-----------+-----------------------+---------------------------------------------------+ |y == x |convertible to bool|== is an equivalence relation over its domain. | +-----------+-----------------------+---------------------------------------------------+ |x != y |convertible to bool|bool(a==b) != bool(a!=b) over its domain. | +-----------+-----------------------+---------------------------------------------------+ |y != x |convertible to bool|bool(a==b) != bool(a!=b) over its domain. | +-----------+-----------------------+---------------------------------------------------+

If X and Y both model Random Access Traversal Iterator then the following additional requirements must be met.

+-----------+-----------------------+---------------------+--------------------------------------+ |Expression |Return Type |Operational Semantics|Assertion/ Precondition | +===========+=======================+=====================+======================================+ |x < y |convertible to bool|y - x > 0 |< is a total ordering relation | +-----------+-----------------------+---------------------+--------------------------------------+ |y < x |convertible to bool|x - y > 0 |< is a total ordering relation | +-----------+-----------------------+---------------------+--------------------------------------+ |x > y |convertible to bool|y < x |> is a total ordering relation | +-----------+-----------------------+---------------------+--------------------------------------+ |y > x |convertible to bool|x < y |> is a total ordering relation | +-----------+-----------------------+---------------------+--------------------------------------+ |x >= y |convertible to bool|!(x < y) | | +-----------+-----------------------+---------------------+--------------------------------------+ |y >= x |convertible to bool|!(y < x) | | +-----------+-----------------------+---------------------+--------------------------------------+ |x <= y |convertible to bool|!(x > y) | | +-----------+-----------------------+---------------------+--------------------------------------+ |y <= x |convertible to bool|!(y > x) | | +-----------+-----------------------+---------------------+--------------------------------------+ |y - x |Distance |distance(Y(x),y) |pre: there exists a value n of | | | | |Distance such that x + n == y.| | | | |y == x + (y - x). | +-----------+-----------------------+---------------------+--------------------------------------+ |x - y |Distance |distance(y,Y(x)) |pre: there exists a value n of | | | | |Distance such that y + n == x.| | | | |x == y + (x - y). | +-----------+-----------------------+---------------------+--------------------------------------+