1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175
|
<HTML>
<!--
-- Copyright (c) 1996,1997
-- Silicon Graphics Computer Systems, Inc.
--
-- Permission to use, copy, modify, distribute and sell this software
-- and its documentation for any purpose is hereby granted without fee,
-- provided that the above copyright notice appears in all copies and
-- that both that copyright notice and this permission notice appear
-- in supporting documentation. Silicon Graphics makes no
-- representations about the suitability of this software for any
-- purpose. It is provided "as is" without express or implied warranty.
--
-- Copyright (c) 1994
-- Hewlett-Packard Company
--
-- Permission to use, copy, modify, distribute and sell this software
-- and its documentation for any purpose is hereby granted without fee,
-- provided that the above copyright notice appears in all copies and
-- that both that copyright notice and this permission notice appear
-- in supporting documentation. Hewlett-Packard Company makes no
-- representations about the suitability of this software for any
-- purpose. It is provided "as is" without express or implied warranty.
--
-->
<Head>
<Title>inner_product</Title>
<!-- Generated by htmldoc -->
</HEAD>
<BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b"
ALINK="#ff0000">
<IMG SRC="CorpID.gif"
ALT="Silicon Graphics, Inc." HEIGHT="43" WIDTH="151">
<!--end header-->
<BR Clear>
<H1>inner_product</H1>
<Table CellPadding=0 CellSpacing=0 width=100%>
<TR>
<TD Align=left><Img src = "algorithms.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD>
<TD Align=right><Img src = "function.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD>
</TR>
<TR>
<TD Align=left VAlign=top><b>Category</b>: algorithms</TD>
<TD Align=right VAlign=top><b>Component type</b>: function</TD>
</TR>
</Table>
<h3>Prototype</h3>
<tt>Inner_product</tt> is an overloaded name; there are actually two
<tt>inner_product</tt> functions.
<pre>
template <class <A href="InputIterator.html">InputIterator</A>1, class <A href="InputIterator.html">InputIterator</A>2, class T>
T inner_product(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, T init);
template <class <A href="InputIterator.html">InputIterator</A>1, class <A href="InputIterator.html">InputIterator</A>2, class T,
class <A href="BinaryFunction.html">BinaryFunction</A>1, class <A href="BinaryFunction.html">BinaryFunction</A>2>
T inner_product(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, T init, BinaryFunction1 binary_op1,
BinaryFunction2 binary_op2);
</pre>
<h3>Description</h3>
<tt>Inner_product</tt> calculates a generalized inner product of the ranges
<tt>[first1, last1)</tt> and <tt>[first2, last2)</tt>.
<P>
The first version of <tt>inner_product</tt> returns
<tt>init</tt> plus the inner product of the two ranges <A href="#1">[1]</A>. That is,
it first initializes the result to <tt>init</tt> and then, for each iterator
<tt>i</tt> in <tt>[first1, last1)</tt>, in order from the beginning to the end
of the range, updates the result by <tt>result = result + (*i)
* *(first2 + (i - first1))</tt>.
<P>
The second version of <tt>inner_product</tt> is identical to the first, except
that it uses two user-supplied <A href="functors.html">function objects</A> instead of
<tt>operator+</tt> and <tt>operator*</tt>. That is,
it first initializes the result to <tt>init</tt> and then, for each iterator
<tt>i</tt> in <tt>[first1, last1)</tt>, in order from the beginning to the end
of the range, updates the result by <tt>result = binary_op1(result,
binary_op2(*i, *(first2 + (i - first1)))</tt>. <A href="#2">[2]</A>
<h3>Definition</h3>
Defined in <A href="algo.h">algo.h</A>.
<h3>Requirements on types</h3>
For the first version:
<UL>
<LI>
<tt>InputIterator1</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.
<LI>
<tt>InputIterator2</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.
<LI>
<tt>T</tt> is a model of <A href="Assignable.html">Assignable</A>.
<LI>
If <tt>x</tt> is an object of type <tt>T</tt>, <tt>y</tt> is an object of
<tt>InputIterator1</tt>'s value type, and <tt>z</tt> is an object
of <tt>InputIterator2</tt>'s value type, then <tt>x + y * z</tt> is defined.
<LI>
The type of <tt>x + y * z</tt> is convertible to <tt>T</tt>.
</UL>
For the second version:
<UL>
<LI>
<tt>InputIterator1</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.
<LI>
<tt>InputIterator2</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.
<LI>
<tt>T</tt> is a model of <A href="Assignable.html">Assignable</A>.
<LI>
<tt>BinaryFunction1</tt> is a model of <A href="BinaryFunction.html">Binary Function</A>.
<LI>
<tt>BinaryFunction2</tt> is a model of <A href="BinaryFunction.html">Binary Function</A>.
<LI>
<tt>InputIterator1</tt>'s value type is convertible to <tt>BinaryFunction2</tt>'s
first argument type.
<LI>
<tt>InputIterator2</tt>'s value type is convertible to <tt>BinaryFunction2</tt>'s
second argument type.
<LI>
<tt>T</tt> is convertible to <tt>BinaryFunction1</tt>'s first argument type.
<LI>
<tt>BinaryFunction2</tt>'s return type is convertible to <tt>BinaryFunction1</tt>'s
second argument type.
<LI>
<tt>BinaryFunction1</tt>'s return type is convertible to <tt>T</tt>.
</UL>
<h3>Preconditions</h3>
<UL>
<LI>
<tt>[first1, last1)</tt> is a valid range.
<LI>
<tt>[first2, first2 + (last1 - first1))</tt> is a valid range.
</UL>
<h3>Complexity</h3>
Linear. Exactly <tt>last1 - first1</tt> applications of each binary operation.
<h3>Example</h3>
<pre>
int main()
{
int A1[] = {1, 2, 3};
int A2[] = {4, 1, -2};
const int N1 = sizeof(A1) / sizeof(int);
cout << "The inner product of A1 and A2 is "
<< inner_product(A1, A1 + N1, A2, 0)
<< endl;
}
</pre>
<h3>Notes</h3>
<P><A name="1">[1]</A>
There are several reasons why it is important that <tt>inner_product</tt>
starts with the value <tt>init</tt>. One of the most basic is that this allows
<tt>inner_product</tt> to have a well-defined result even if <tt>[first1, last1)</tt> is
an empty range: if it is empty, the return value is <tt>init</tt>.
The ordinary inner product corresponds to setting <tt>init</tt> to 0.
<P><A name="2">[2]</A>
Neither binary operation is required to be either associative or
commutative: the order of all operations is specified.
<h3>See also</h3>
<tt><A href="accumulate.html">accumulate</A></tt>, <tt><A href="partial_sum.html">partial_sum</A></tt>, <tt><A href="adjacent_difference.html">adjacent_difference</A></tt>,
<tt><A href="count.html">count</A></tt>
<!--start footer-->
<HR SIZE="6">
<A href="http://www.sgi.com/"><IMG SRC="surf.gif" HEIGHT="54" WIDTH="54"
ALT="[Silicon Surf]"></A>
<A HREF="index.html"><IMG SRC="stl_home.gif"
HEIGHT="54" WIDTH="54" ALT="[STL Home]"></A>
<BR>
<FONT SIZE="-2">
<A href="http://www.sgi.com/Misc/sgi_info.html" TARGET="_top">Copyright ©
1996 Silicon Graphics, Inc.</A> All Rights Reserved.</FONT>
<FONT SIZE="-3"><a href="http://www.sgi.com/Misc/external.list.html" TARGET="_top">TrademarkInformation</A>
</FONT>
<P>
</BODY>
</HTML>
|