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| <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)" /> |
| <meta name="KEYWORDS" content="libstdc++, libstdc++-v3, GCC, g++, STL, SGI" /> |
| <meta name="DESCRIPTION" content="SGI extensions preserved in libstdc++-v3." /> |
| <meta name="GENERATOR" content="vi and eight fingers" /> |
| <title>SGI extensions to the library in libstdc++-v3</title> |
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| |
| <h1 class="centered"><a name="top">SGI extensions to the library in |
| libstdc++-v3</a></h1> |
| |
| <p>This page describes the extensions that SGI made to their version of the |
| STL subset of the Standard C++ Library. For a time we |
| <a href="../faq/index.html#5_3">tracked and imported changes and updates |
| from most of the SGI STL</a>, up through their (apparently) final release. |
| Their extensions were mostly preserved. |
| </p> |
| |
| <p>They are listed according to the chapters of the library that they |
| extend (see <a href="../documentation.html#3">the chapter-specific notes</a> |
| for a description). Not every chapter may have extensions, and the |
| extensions may come and go. Also, this page is incomplete because the |
| author is pressed for time. Check back often; the latest change was on |
| $Date: 2003/04/16 17:02:47 $ (UTC). |
| </p> |
| |
| <p>Descriptions range from the scanty to the verbose. You should also check |
| the <a href="../documentation.html#4">generated documentation</a> for notes |
| and comments, especially for entries marked with '*'. For more complete |
| doumentation, see the SGI website. For <em>really</em> complete |
| documentation, buy a copy of Matt Austern's book. *grin* |
| </p> |
| |
| <p>Back to the <a href="howto.html">libstdc++-v3 extensions</a>. |
| </p> |
| |
| |
| <!-- ####################################################### --> |
| <hr /> |
| <h3><a name="ch20">Chapter 20</a></h3> |
| <p>The <functional> header contains many additional functors and |
| helper functions, extending section 20.3. They are implemented in the |
| file stl_function.h: |
| </p> |
| <ul> |
| <li><code>identity_element</code> for addition and multiplication. * </li> |
| <li>The functor <code>identity</code>, whose <code>operator()</code> |
| returns the argument unchanged. * </li> |
| <li>Composition functors <code>unary_function</code> and |
| <code>binary_function</code>, and their helpers <code>compose1</code> |
| and <code>compose2</code>. * </li> |
| <li><code>select1st</code> and <code>select2nd</code>, to strip pairs. * </li> |
| <li><code>project1st</code> and <code>project2nd</code>. * </li> |
| <li>A set of functors/functions which always return the same result. They |
| are <code>constant_void_fun</code>, <code>constant_binary_fun</code>, |
| <code>constant_unary_fun</code>, <code>constant0</code>, |
| <code>constant1</code>, and <code>constant2</code>. * </li> |
| <li>The class <code>subtractive_rng</code>. * </li> |
| <li>mem_fun adaptor helpers <code>mem_fun1</code> and |
| <code>mem_fun1_ref</code> are provided for backwards compatibility. </li> |
| </ul> |
| <p>20.4.1 can use several different allocators; they are described on the |
| main extensions page. |
| </p> |
| <p>20.4.3 is extended with a special version of |
| <code>get_temporary_buffer</code> taking a second argument. The argument |
| is a pointer, which is ignored, but can be used to specify the template |
| type (instead of using explicit function template arguments like the |
| standard version does). That is, in addition to |
| </p> |
| <pre> |
| get_temporary_buffer<int>(5);</pre> |
| you can also use |
| <pre> |
| get_temporary_buffer(5, (int*)0);</pre> |
| <p>A class <code>temporary_buffer</code> is given in stl_tempbuf.h. * |
| </p> |
| <p>The specialized algorithms of section 20.4.4 are extended with |
| <code>uninitialized_copy_n</code>. * |
| </p> |
| <p>Return <a href="howto.html">to the main extensions page</a> or |
| <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>. |
| </p> |
| |
| |
| <hr /> |
| <h3><a name="ch23">Chapter 23</a></h3> |
| <p>A few extensions and nods to backwards-compatibility have been made with |
| containers. Those dealing with older SGI-style allocators are dealt with |
| elsewhere. The remaining ones all deal with bits: |
| </p> |
| <p>The old pre-standard <code>bit_vector</code> class is present for |
| backwards compatibility. It is simply a typedef for the |
| <code>vector<bool></code> specialization. |
| </p> |
| <p>The <code>bitset</code> class has a number of extensions, described in the |
| rest of this item. First, we'll mention that this implementation of |
| <code>bitset<N></code> is specialized for cases where N number of |
| bits will fit into a single word of storage. If your choice of N is |
| within that range (<=32 on i686-pc-linux-gnu, for example), then all |
| of the operations will be faster. |
| </p> |
| <p>There are |
| versions of single-bit test, set, reset, and flip member functions which |
| do no range-checking. If we call them member functions of an instantiation |
| of "bitset<N>," then their names and signatures are: |
| </p> |
| <pre> |
| bitset<N>& _Unchecked_set (size_t pos); |
| bitset<N>& _Unchecked_set (size_t pos, int val); |
| bitset<N>& _Unchecked_reset (size_t pos); |
| bitset<N>& _Unchecked_flip (size_t pos); |
| bool _Unchecked_test (size_t pos);</pre> |
| <p>Note that these may in fact be removed in the future, although we have |
| no present plans to do so (and there doesn't seem to be any immediate |
| reason to). |
| </p> |
| <p>The semantics of member function <code>operator[]</code> are not specified |
| in the C++ standard. A long-standing defect report calls for sensible |
| obvious semantics, which are already implemented here: <code>op[]</code> |
| on a const bitset returns a bool, and for a non-const bitset returns a |
| <code>reference</code> (a nested type). However, this implementation does |
| no range-checking on the index argument, which is in keeping with other |
| containers' <code>op[]</code> requirements. The defect report's proposed |
| resolution calls for range-checking to be done. We'll just wait and see... |
| </p> |
| <p>Finally, two additional searching functions have been added. They return |
| the index of the first "on" bit, and the index of the first |
| "on" bit that is after <code>prev</code>, respectively: |
| </p> |
| <pre> |
| size_t _Find_first() const; |
| size_t _Find_next (size_t prev) const;</pre> |
| <p>The same caveat given for the _Unchecked_* functions applies here also. |
| </p> |
| <p>Return <a href="howto.html">to the main extensions page</a> or |
| <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>. |
| </p> |
| |
| |
| <hr /> |
| <h3><a name="ch24">Chapter 24</a></h3> |
| <p>24.3.2 describes <code>struct iterator</code>, which didn't exist in the |
| original HP STL implementation (the language wasn't rich enough at the |
| time). For backwards compatibility, base classes are provided which |
| declare the same nested typedefs: |
| </p> |
| <ul> |
| <li>input_iterator</li> |
| <li>output_iterator</li> |
| <li>forward_iterator</li> |
| <li>bidirectional_iterator</li> |
| <li>random_access_iterator</li> |
| </ul> |
| <p>24.3.4 describes iterator operation <code>distance</code>, which takes |
| two iterators and returns a result. It is extended by another signature |
| which takes two iterators and a reference to a result. The result is |
| modified, and the function returns nothing. |
| </p> |
| <p>Return <a href="howto.html">to the main extensions page</a> or |
| <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>. |
| </p> |
| |
| |
| <hr /> |
| <h3><a name="ch25">Chapter 25</a></h3> |
| <p>25.1.6 (count, count_if) is extended with two more versions of count |
| and count_if. The standard versions return their results. The |
| additional signatures return void, but take a final parameter by |
| reference to which they assign their results, e.g., |
| </p> |
| <pre> |
| void count (first, last, value, n);</pre> |
| <p>25.2 (mutating algorithms) is extended with two families of signatures, |
| random_sample and random_sample_n. |
| </p> |
| <p>25.2.1 (copy) is extended with |
| </p> |
| <pre> |
| copy_n (_InputIter first, _Size count, _OutputIter result);</pre> |
| <p>which copies the first 'count' elements at 'first' into 'result'. |
| </p> |
| <p>25.3 (sorting 'n' heaps 'n' stuff) is extended with some helper |
| predicates. Look in the doxygen-generated pages for notes on these. |
| </p> |
| <ul> |
| <li><code>is_heap</code> tests whether or not a range is a heap.</li> |
| <li><code>is_sorted</code> tests whether or not a range is sorted in |
| nondescending order.</li> |
| </ul> |
| <p>25.3.8 (lexigraphical_compare) is extended with |
| </p> |
| <pre> |
| lexicographical_compare_3way(_InputIter1 first1, _InputIter1 last1, |
| _InputIter2 first2, _InputIter2 last2)</pre> |
| <p>which does... what? |
| </p> |
| <p>Return <a href="howto.html">to the main extensions page</a> or |
| <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>. |
| </p> |
| |
| |
| <hr /> |
| <h3><a name="ch26">Chapter 26</a></h3> |
| <p>26.4, the generalized numeric operations such as accumulate, are extended |
| with the following functions: |
| </p> |
| <pre> |
| power (x, n); |
| power (x, n, moniod_operation);</pre> |
| <p>Returns, in FORTRAN syntax, "x ** n" where n>=0. In the |
| case of n == 0, returns the <a href="#ch20">identity element</a> for the |
| monoid operation. The two-argument signature uses multiplication (for |
| a true "power" implementation), but addition is supported as well. |
| The operation functor must be associative. |
| </p> |
| <p>The <code>iota</code> function wins the award for Extension With the |
| Coolest Name. It "assigns sequentially increasing values to a range. |
| That is, it assigns value to *first, value + 1 to *(first + 1) and so |
| on." Quoted from SGI documentation. |
| </p> |
| <pre> |
| void iota(_ForwardIter first, _ForwardIter last, _Tp value);</pre> |
| <p>Return <a href="howto.html">to the main extensions page</a> or |
| <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>. |
| </p> |
| |
| |
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| <p class="fineprint"><em> |
| See <a href="../17_intro/license.html">license.html</a> for copying conditions. |
| Comments and suggestions are welcome, and may be sent to |
| <a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>. |
| </em></p> |
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