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Document operator==/operator!= as undefined if the equality predicates aren't equivalent. Fixes #2237.

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[SVN r49925]
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Daniel James
2008-11-24 22:55:47 +00:00
parent 527a72860d
commit d022cc48ad
3 changed files with 30 additions and 0 deletions
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4
doc/changes.qbk
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@ -45,5 +45,9 @@ First official release.
[h2 Boost 1.38.0]
* Use [@../../libs/utility/swap.html `boost::swap`].
* [@https://svn.boost.org/trac/boost/ticket/2237 Ticket 2237]:
Document that the equality and inequality operators are undefined for two
objects if their equality predicates aren't equivalent. Thanks to Daniel
Krügler.
[endsect]

10
doc/hash_equality.qbk
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@ -41,6 +41,16 @@ This is a simplified version of the example at
[@../../libs/unordered/examples/case_insensitive.hpp /libs/unordered/examples/case_insensitive.hpp]
which supports other locales and string types.
[caution
Be careful when using the equality (`==`) operator with custom equality
predicates, especially if you're using a function pointer. If you compare two
containers with different equality predicates then the result is undefined.
For most stateless function objects this is impossible - since you can only
compare objects with the same equality predicate you know the equality
predicates must be equal. But if you're using function pointers or a stateful
equality predicate (e.g. boost::function) then you can get into trouble.
]
[h2 Custom Types]
Similarly, a custom hash function can be used for custom types:

16
doc/ref.xml
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@ -678,6 +678,8 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<type>bool</type>
<notes>
<para>This is a boost extension.</para>
<para>Behavior is undefined if the two containers don't have
equivalent equality predicates.</para>
</notes>
</function>
<function name="operator!=">
@ -700,6 +702,8 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<type>bool</type>
<notes>
<para>This is a boost extension.</para>
<para>Behavior is undefined if the two containers don't have
equivalent equality predicates.</para>
</notes>
</function>
</free-function-group>
@ -1406,6 +1410,8 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<type>bool</type>
<notes>
<para>This is a boost extension.</para>
<para>Behavior is undefined if the two containers don't have
equivalent equality predicates.</para>
</notes>
</function>
<function name="operator!=">
@ -1428,6 +1434,8 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<type>bool</type>
<notes>
<para>This is a boost extension.</para>
<para>Behavior is undefined if the two containers don't have
equivalent equality predicates.</para>
</notes>
</function>
</free-function-group>
@ -2185,6 +2193,8 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<type>bool</type>
<notes>
<para>This is a boost extension.</para>
<para>Behavior is undefined if the two containers don't have
equivalent equality predicates.</para>
</notes>
</function>
<function name="operator!=">
@ -2209,6 +2219,8 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<type>bool</type>
<notes>
<para>This is a boost extension.</para>
<para>Behavior is undefined if the two containers don't have
equivalent equality predicates.</para>
</notes>
</function>
</free-function-group>
@ -2927,6 +2939,8 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<type>bool</type>
<notes>
<para>This is a boost extension.</para>
<para>Behavior is undefined if the two containers don't have
equivalent equality predicates.</para>
</notes>
</function>
<function name="operator!=">
@ -2951,6 +2965,8 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<type>bool</type>
<notes>
<para>This is a boost extension.</para>
<para>Behavior is undefined if the two containers don't have
equivalent equality predicates.</para>
</notes>
</function>
</free-function-group>