<?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <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> <link rel="StyleSheet" href="../lib3styles.css" type="text/css" /> <link rel="Start" href="../documentation.html" type="text/html" title="GNU C++ Standard Library" /> <link rel="Subsection" href="sgiexts.html" type="text/html" title="Extensions" /> <link rel="Bookmark" href="howto.html" type="text/html" title="Extensions" /> <link rel="Copyright" href="../17_intro/license.html" type="text/html" /> </head> <body> <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> <!-- ####################################################### --> <hr /> <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> </body> </html>