boostorg/unordered
1
0
Fork 1
mirror of https://github.com/boostorg/unordered.git synced 2025-07-29 19:07:15 +02:00
Code Issues Packages Projects Releases Wiki Activity

Merge some documentation updates and fixes from trunk.

Browse Source 
Merged revisions 47364,47402-47403 via svnmerge from 
https://svn.boost.org/svn/boost/trunk

........
  r47364 | danieljames | 2008-07-12 20:32:15 +0100 (Sat, 12 Jul 2008) | 1 line
  
  Fix a PDF link that I missed before. (in static assert)
........
  r47402 | danieljames | 2008-07-13 20:42:56 +0100 (Sun, 13 Jul 2008) | 2 lines
  
  Note that emplace is only available on a few compilers.
........
  r47403 | danieljames | 2008-07-13 21:07:45 +0100 (Sun, 13 Jul 2008) | 2 lines
  
  Update the implementation details.
........


[SVN r47405]
This commit is contained in:
Daniel James
2008-07-13 21:08:33 +00:00
parent 4e4f99d51f
commit f20f72bade
2 changed files with 23 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

37
doc/rationale.qbk
View File

@ -96,6 +96,17 @@ efficiency advantage of power of 2 hash tables.
So, this implementation uses a prime number for the hash table size.
[h2 Equality operators and hash functions]
`operator==` and `operator!=` are not included in the standard, but I've
added them as I think they could be useful and can be efficiently
implemented. They are specified
differently to the standard associative containers, comparing keys
using the equality predicate rather than `operator==`. This is inconsistent
with the other containers but it is probably closer to user's expectations.
I have also added a `hash_value` free function so that the containers can be
hashed by [classref boost::hash].
[h2 Active Issues and Proposals]
[h3 Removing unused allocator functions]
@ -181,32 +192,14 @@ It is not specified if `unordered_multiset` and `unordered_multimap` preserve th
of elements with equivalent keys (i.e. if they're stable under `insert` and `erase`).
This is [@http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#518 issue 581].
The current proposal is that insert, erase and rehash are stable - so they are here.
(Update: during the release of this version, this requirement was added to
[@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2691.pdf
the lastest working draft]).
[h3 const_local_iterator cbegin, cend missing from TR1]
[@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2482.html#691
[@http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2684.html#691
Issue 691] is that `cbegin` and `cend` are missing for local iterators.
The current resolution is that they'll be added, so I've added them.
[h2 Future Developments]
[h3 Support for `emplace`]
In __n2369__ a new member function, `emplace` was added to the containers to
allow placement insert, as described in __n2345__. To fully implement this
`std::forward` is required, along with new functions in `std::allocator` and
new constructors in `std::pair`. But partial support is possible - especially
if I don't use the `construct` member of allocators.
[h3 Equality operator]
While `operator==` and `operator!=` are not included in the standard, it's
possible to implement them for all the containers - this is helped by having
stable order of elements with equivalent keys. They will need to be specified
differently to the standard associative containers, probably comparing keys
using the equality predicate rather than `operator==`. This is inconsistent
with the other containers but it is probably closer to user's expectations.
If these are added then a `hash_value` free function should also be added.
[endsect]

8
doc/ref.xml
View File

@ -284,6 +284,7 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<notes>
<para>Can invalidate iterators, but only if the insert causes the load factor to be greater to or equal to the maximum load factor.</para>
<para>Pointers and references to elements are never invalidated.</para>
<para>Only available on compilers with support for variadic template arguments and rvalue references.</para>
</notes>
</method>
<method name="emplace">
@ -312,6 +313,7 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<para>The standard is fairly vague on the meaning of the hint. But the only practical way to use it, and the only way that Boost.Unordered supports is to point to an existing element with the same value. </para>
<para>Can invalidate iterators, but only if the insert causes the load factor to be greater to or equal to the maximum load factor.</para>
<para>Pointers and references to elements are never invalidated.</para>
<para>Only available on compilers with support for variadic template arguments and rvalue references.</para>
</notes>
</method>
<method name="insert">
@ -1030,6 +1032,7 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<notes>
<para>Can invalidate iterators, but only if the insert causes the load factor to be greater to or equal to the maximum load factor.</para>
<para>Pointers and references to elements are never invalidated.</para>
<para>Only available on compilers with support for variadic template arguments and rvalue references.</para>
</notes>
</method>
<method name="emplace">
@ -1058,6 +1061,7 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<para>The standard is fairly vague on the meaning of the hint. But the only practical way to use it, and the only way that Boost.Unordered supports is to point to an existing element with the same value. </para>
<para>Can invalidate iterators, but only if the insert causes the load factor to be greater to or equal to the maximum load factor.</para>
<para>Pointers and references to elements are never invalidated.</para>
<para>Only available on compilers with support for variadic template arguments and rvalue references.</para>
</notes>
</method>
<method name="insert">
@ -1788,6 +1792,7 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<notes>
<para>Can invalidate iterators, but only if the insert causes the load factor to be greater to or equal to the maximum load factor.</para>
<para>Pointers and references to elements are never invalidated.</para>
<para>Only available on compilers with support for variadic template arguments and rvalue references.</para>
</notes>
</method>
<method name="emplace">
@ -1816,6 +1821,7 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<para>The standard is fairly vague on the meaning of the hint. But the only practical way to use it, and the only way that Boost.Unordered supports is to point to an existing element with the same key. </para>
<para>Can invalidate iterators, but only if the insert causes the load factor to be greater to or equal to the maximum load factor.</para>
<para>Pointers and references to elements are never invalidated.</para>
<para>Only available on compilers with support for variadic template arguments and rvalue references.</para>
</notes>
</method>
<method name="insert">
@ -2585,6 +2591,7 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<notes>
<para>Can invalidate iterators, but only if the insert causes the load factor to be greater to or equal to the maximum load factor.</para>
<para>Pointers and references to elements are never invalidated.</para>
<para>Only available on compilers with support for variadic template arguments and rvalue references.</para>
</notes>
</method>
<method name="emplace">
@ -2613,6 +2620,7 @@ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
<para>The standard is fairly vague on the meaning of the hint. But the only practical way to use it, and the only way that Boost.Unordered supports is to point to an existing element with the same key. </para>
<para>Can invalidate iterators, but only if the insert causes the load factor to be greater to or equal to the maximum load factor.</para>
<para>Pointers and references to elements are never invalidated.</para>
<para>Only available on compilers with support for variadic template arguments and rvalue references.</para>
</notes>
</method>
<method name="insert">