2006-09-11 22:27:29 +00:00
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.. Copyright David Abrahams 2006. Distributed under the Boost
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.. Software License, Version 1.0. (See accompanying
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.. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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2004-01-27 17:03:46 +00:00
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Interoperable Iterator Concept
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..............................
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A class or built-in type ``X`` that models Single Pass Iterator is
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*interoperable with* a class or built-in type ``Y`` that also models
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Single Pass Iterator if the following expressions are valid and
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respect the stated semantics. In the tables below, ``x`` is an object
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of type ``X``, ``y`` is an object of type ``Y``, ``Distance`` is
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``iterator_traits<Y>::difference_type``, and ``n`` represents a
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constant object of type ``Distance``.
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+-----------+-----------------------+---------------------------------------------------+
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|Expression |Return Type |Assertion/Precondition/Postcondition |
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+===========+=======================+===================================================+
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|``y = x`` |``Y`` |post: ``y == x`` |
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+-----------+-----------------------+---------------------------------------------------+
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|``Y(x)`` |``Y`` |post: ``Y(x) == x`` |
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+-----------+-----------------------+---------------------------------------------------+
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|``x == y`` |convertible to ``bool``|``==`` is an equivalence relation over its domain. |
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+-----------+-----------------------+---------------------------------------------------+
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|``y == x`` |convertible to ``bool``|``==`` is an equivalence relation over its domain. |
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+-----------+-----------------------+---------------------------------------------------+
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|``x != y`` |convertible to ``bool``|``bool(a==b) != bool(a!=b)`` over its domain. |
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+-----------+-----------------------+---------------------------------------------------+
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|``y != x`` |convertible to ``bool``|``bool(a==b) != bool(a!=b)`` over its domain. |
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+-----------+-----------------------+---------------------------------------------------+
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If ``X`` and ``Y`` both model Random Access Traversal Iterator then
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the following additional requirements must be met.
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+-----------+-----------------------+---------------------+--------------------------------------+
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|Expression |Return Type |Operational Semantics|Assertion/ Precondition |
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+===========+=======================+=====================+======================================+
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|``x < y`` |convertible to ``bool``|``y - x > 0`` |``<`` is a total ordering relation |
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+-----------+-----------------------+---------------------+--------------------------------------+
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|``y < x`` |convertible to ``bool``|``x - y > 0`` |``<`` is a total ordering relation |
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+-----------+-----------------------+---------------------+--------------------------------------+
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|``x > y`` |convertible to ``bool``|``y < x`` |``>`` is a total ordering relation |
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+-----------+-----------------------+---------------------+--------------------------------------+
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|``y > x`` |convertible to ``bool``|``x < y`` |``>`` is a total ordering relation |
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+-----------+-----------------------+---------------------+--------------------------------------+
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|``x >= y`` |convertible to ``bool``|``!(x < y)`` | |
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+-----------+-----------------------+---------------------+--------------------------------------+
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|``y >= x`` |convertible to ``bool``|``!(y < x)`` | |
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+-----------+-----------------------+---------------------+--------------------------------------+
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|``x <= y`` |convertible to ``bool``|``!(x > y)`` | |
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+-----------+-----------------------+---------------------+--------------------------------------+
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|``y <= x`` |convertible to ``bool``|``!(y > x)`` | |
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+-----------+-----------------------+---------------------+--------------------------------------+
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|``y - x`` |``Distance`` |``distance(Y(x),y)`` |pre: there exists a value ``n`` of |
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| | | |``Distance`` such that ``x + n == y``.|
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| | | |``y == x + (y - x)``. |
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+-----------+-----------------------+---------------------+--------------------------------------+
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|``x - y`` |``Distance`` |``distance(y,Y(x))`` |pre: there exists a value ``n`` of |
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| | | |``Distance`` such that ``y + n == x``.|
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| | | |``x == y + (x - y)``. |
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+-----------+-----------------------+---------------------+--------------------------------------+
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