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added Interoperable Iterators

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[SVN r21698]
This commit is contained in:
Jeremy Siek
2004-01-13 19:21:18 +00:00
parent 0f8aa07e5c
commit 80f6a13e79
3 changed files with 271 additions and 35 deletions
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doc/new-iter-concepts.rst
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@ -291,6 +291,13 @@ reason for the fine grain slicing of the concepts into the
Incrementable and Single Pass is to provide concepts that are exact
matches with the original input and output iterator requirements.
This proposal also includes a concept for specifying when an iterator
is interoperable with another iterator, in the sense that ``int*`` is
interoperable with ``int const*``.
- Interoperable Iterators
The relationship between the new iterator concepts and the old are
given in the following diagram.
@ -657,6 +664,79 @@ constant object of type ``Distance``.
random_access_traversal_tag for consistency
Interoperable Iterators [lib.interoperable.iterators]
-----------------------------------------------------
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 both ``X`` and ``Y`` have the same difference
type and traversal tag and 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<X>::difference_type``, and ``n`` represents a
constant object of type ``Distance``.
If the traversal tag for ``X`` and ``Y`` is convertible to
``single_pass_traversal_tag`` then the following requirements must be
met.
+-------------------------------------------+-------------------------------------------------+---------------------------------------------------+
|Expression |Return Type |Assertion/Precondition/Postcondition |
+===========================================+=================================================+===================================================+
|``y = x`` |``Y`` |post: ``y == 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 the traversal tag for ``X`` and ``Y`` is convertible to
``random_access_traversal_tag`` then the following 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`` |``x < y ? distance(x,y) |pre: there exists a |
| | |: -distance(y,x)`` |value ``n`` of |
| | | |``Distance`` such that|
| | | |``x + n == y``. ``y |
| | | |== x + (y - x)``. |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
|``x - y`` |``Distance`` |``y < x ? distance(y,x) |pre: there exists a |
| | |: -distance(x,y)`` |value ``n`` of |
| | | |``Distance`` such that|
| | | |``y + n == x``. ``x |
| | | |== y + (x - y)``. |
+-------------------------------------------+-------------------------------------------------+-------------------------+----------------------+
Addition to [lib.iterator.synopsis]
===================================