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8 <meta name="AUTHOR" content="pme@gcc.gnu.org (Phil Edwards)" />
9 <meta name="KEYWORDS" content="libstdc++, libstdc++-v3, GCC, g++, STL, SGI" />
10 <meta name="DESCRIPTION" content="SGI extensions preserved in libstdc++-v3." />
11 <meta name="GENERATOR" content="vi and eight fingers" />
12 <title>SGI extensions to the library in libstdc++-v3</title>
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17 <h1 class="centered"><a name="top">SGI extensions to the library in
20 <p>This page describes the extensions that SGI made to their version of the
21 STL subset of the Standard C++ Library. For a time we
22 <a href="../faq/index.html#5_3">tracked and imported changes and updates
23 from most of the SGI STL</a>, up through their (apparently) final release.
24 Their extensions were mostly preserved.
27 <p>They are listed according to the chapters of the library that they
28 extend (see <a href="../documentation.html#3">the chapter-specific notes</a>
29 for a description). Not every chapter may have extensions, and the
30 extensions may come and go. Also, this page is incomplete because the
31 author is pressed for time. Check back often; the latest change was on
32 $Date: 2002/11/17 17:15:06 $ (UTC).
35 <p>Descriptions range from the scanty to the verbose. You should also check
36 the <a href="../documentation.html#4">generated documentation</a> for notes
37 and comments, especially for entries marked with '*'. For more complete
38 doumentation, see the SGI website. For <em>really</em> complete
39 documentation, buy a copy of Matt Austern's book. *grin*
42 <p>Back to the <a href="howto.html">libstdc++-v3 extensions</a>.
46 <!-- ####################################################### -->
48 <h3><a name="ch20">Chapter 20</a></h3>
49 <p>The <functional> header contains many additional functors and
50 helper functions, extending section 20.3. They are implemented in the
54 <li><code>identity_element</code> for addition and multiplication. * </li>
55 <li>The functor <code>identity</code>, whose <code>operator()</code>
56 returns the argument unchanged. * </li>
57 <li>Composition functors <code>unary_function</code> and
58 <code>binary_function</code>, and their helpers <code>compose1</code>
59 and <code>compose2</code>. * </li>
60 <li><code>select1st</code> and <code>select2nd</code>, to strip pairs. * </li>
61 <li><code>project1st</code> and <code>project2nd</code>. * </li>
62 <li>A set of functors/functions which always return the same result. They
63 are <code>constant_void_fun</code>, <code>constant_binary_fun</code>,
64 <code>constant_unary_fun</code>, <code>constant0</code>,
65 <code>constant1</code>, and <code>constant2</code>. * </li>
66 <li>The class <code>subtractive_rng</code>. * </li>
67 <li>mem_fun adaptor helpers <code>mem_fun1</code> and
68 <code>mem_fun1_ref</code> are provided for backwards compatibility. </li>
70 <p>20.4.1 can use several different allocators; they are described on the
73 <p>20.4.3 is extended with a special version of
74 <code>get_temporary_buffer</code> taking a second argument. The argument
75 is a pointer, which is ignored, but can be used to specify the template
76 type (instead of using explicit function template arguments like the
77 standard version does). That is, in addition to
80 get_temporary_buffer<int>(5);</pre>
83 get_temporary_buffer(5, (int*)0);</pre>
84 <p>A class <code>temporary_buffer</code> is given in stl_tempbuf.h. *
86 <p>The specialized algorithms of section 20.4.4 are extended with
87 <code>uninitialized_copy_n</code>. *
89 <p>Return <a href="howto.html">to the main extensions page</a> or
90 <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>.
95 <h3><a name="ch23">Chapter 23</a></h3>
96 <p>A few extensions and nods to backwards-compatibility have been made with
97 containers. Those dealing with older SGI-style allocators are dealt with
98 elsewhere. The remaining ones all deal with bits:
100 <p>The old pre-standard <code>bit_vector</code> class is present for
101 backwards compatibility. It is simply a typedef for the
102 <code>vector<bool></code> specialization.
104 <p>The <code>bitset</code> class has a number of extensions, described in the
105 rest of this item. First, we'll mention that this implementation of
106 <code>bitset<N></code> is specialized for cases where N number of
107 bits will fit into a single word of storage. If your choice of N is
108 within that range (<=32 on i686-pc-linux-gnu, for example), then all
109 of the operations will be faster.
112 versions of single-bit test, set, reset, and flip member functions which
113 do no range-checking. If we call them member functions of an instantiation
114 of "bitset<N>," then their names and signatures are:
117 bitset<N>& _Unchecked_set (size_t pos);
118 bitset<N>& _Unchecked_set (size_t pos, int val);
119 bitset<N>& _Unchecked_reset (size_t pos);
120 bitset<N>& _Unchecked_flip (size_t pos);
121 bool _Unchecked_test (size_t pos);</pre>
122 <p>Note that these may in fact be removed in the future, although we have
123 no present plans to do so (and there doesn't seem to be any immediate
126 <p>The semantics of member function <code>operator[]</code> are not specified
127 in the C++ standard. A long-standing defect report calls for sensible
128 obvious semantics, which are already implemented here: <code>op[]</code>
129 on a const bitset returns a bool, and for a non-const bitset returns a
130 <code>reference</code> (a nested type). However, this implementation does
131 no range-checking on the index argument, which is in keeping with other
132 containers' <code>op[]</code> requirements. The defect report's proposed
133 resolution calls for range-checking to be done. We'll just wait and see...
135 <p>Finally, two additional searching functions have been added. They return
136 the index of the first "on" bit, and the index of the first
137 "on" bit that is after <code>prev</code>, respectively:
140 size_t _Find_first() const;
141 size_t _Find_next (size_t prev) const;</pre>
142 <p>The same caveat given for the _Unchecked_* functions applies here also.
144 <p>Return <a href="howto.html">to the main extensions page</a> or
145 <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>.
150 <h3><a name="ch24">Chapter 24</a></h3>
151 <p>24.3.2 describes <code>struct iterator</code>, which didn't exist in the
152 original HP STL implementation (the language wasn't rich enough at the
153 time). For backwards compatibility, base classes are provided which
154 declare the same nested typedefs:
157 <li>input_iterator</li>
158 <li>output_iterator</li>
159 <li>forward_iterator</li>
160 <li>bidirectional_iterator</li>
161 <li>random_access_iterator</li>
163 <p>24.3.4 describes iterator operation <code>distance</code>, which takes
164 two iterators and returns a result. It is extended by another signature
165 which takes two iterators and a reference to a result. The result is
166 modified, and the function returns nothing.
168 <p>Return <a href="howto.html">to the main extensions page</a> or
169 <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>.
174 <h3><a name="ch25">Chapter 25</a></h3>
175 <p>25.1.6 (count, count_if) is extended with two more versions of count
176 and count_if. The standard versions return their results. The
177 additional signatures return void, but take a final parameter by
178 reference to which they assign their results, e.g.,
181 void count (first, last, value, n);</pre>
182 <p>25.2 (mutating algorithms) is extended with two families of signatures,
183 random_sample and random_sample_n.
185 <p>25.2.1 (copy) is extended with
188 copy_n (_InputIter first, _Size count, _OutputIter result);</pre>
189 <p>which copies the first 'count' elements at 'first' into 'result'.
191 <p>25.3 (sorting 'n' heaps 'n' stuff) is extended with some helper
192 predicates. Look in the doxygen-generated pages for notes on these.
195 <li><code>is_heap</code> tests whether or not a range is a heap.</li>
196 <li><code>is_sorted</code> tests whether or not a range is sorted in
197 nondescending order.</li>
199 <p>25.3.8 (lexigraphical_compare) is extended with
202 lexicographical_compare_3way(_InputIter1 first1, _InputIter1 last1,
203 _InputIter2 first2, _InputIter2 last2)</pre>
204 <p>which does... what?
206 <p>Return <a href="howto.html">to the main extensions page</a> or
207 <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>.
212 <h3><a name="ch26">Chapter 26</a></h3>
213 <p>26.4, the generalized numeric operations such as accumulate, are extended
214 with the following functions:
218 power (x, n, moniod_operation);</pre>
219 <p>Returns, in FORTRAN syntax, "x ** n" where n>=0. In the
220 case of n == 0, returns the <a href="#ch20">identity element</a> for the
221 monoid operation. The two-argument signature uses multiplication (for
222 a true "power" implementation), but addition is supported as well.
223 The operation functor must be associative.
225 <p>The <code>iota</code> function wins the award for Extension With the
226 Coolest Name. It "assigns sequentially increasing values to a range.
227 That is, it assigns value to *first, value + 1 to *(first + 1) and so
228 on." Quoted from SGI documentation.
231 void iota(_ForwardIter first, _ForwardIter last, _Tp value);</pre>
232 <p>Return <a href="howto.html">to the main extensions page</a> or
233 <a href="http://gcc.gnu.org/libstdc++/">to the homepage</a>.
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241 See <a href="../17_intro/license.html">license.html</a> for copying conditions.
242 Comments and suggestions are welcome, and may be sent to
243 <a href="mailto:libstdc++@gcc.gnu.org">the libstdc++ mailing list</a>.