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<HTML><!-- -- Copyright (c) 1996-1999 -- 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. 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It is provided "as is" without express or implied warranty. -- --><Head><Title>partial_sum</Title><!-- Generated by htmldoc --></HEAD><BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" ALINK="#ff0000"> <IMG SRC="CorpID.gif" ALT="SGI" HEIGHT="43" WIDTH="151"> <!--end header--><BR Clear><H1>partial_sum</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>Partial_sum</tt> is an overloaded name; there are actually two <tt>partial_sum</tt>functions.<pre>template <class InputIterator, class OutputIterator>OutputIterator partial_sum(InputIterator first, InputIterator last, OutputIterator result);template <class InputIterator, class OutputIterator, class BinaryOperation>OutputIterator partial_sum(InputIterator first, InputIterator last, OutputIterator result, BinaryOperation binary_op);</pre> <h3>Description</h3><tt>Partial_sum</tt> calculates a generalized partial sum: <tt>*first</tt> is assignedto <tt>*result</tt>, the sum of <tt>*first</tt> and <tt>*(first + 1)</tt> is assigned to <tt>*(result + 1)</tt>, and so on. <A href="#1">[1]</A><P>More precisely, a running sum is first initialized to <tt>*first</tt> andassigned to <tt>*result</tt>. For each iterator <tt>i</tt> in <tt>[first + 1, last)</tt>, inorder from beginning to end, the sum is updated by <tt>sum = sum + *i</tt>(in the first version) or <tt>sum = binary_op(sum, *i)</tt> (in the secondversion) and is assigned to <tt>*(result + (i - first))</tt>. <A href="#2">[2]</A><h3>Definition</h3>Defined in the standard header <A href="numeric">numeric</A>, and in the nonstandardbackward-compatibility header <A href="algo.h">algo.h</A>.<h3>Requirements on types</h3>For the first version:<UL><LI><tt>InputIterator</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.<LI><tt>OutputIterator</tt> is a model of <A href="OutputIterator.html">Output Iterator</A>.<LI>If <tt>x</tt> and <tt>y</tt> are objects of <tt>InputIterator</tt>'s value type, then <tt>x + y</tt> is defined.<LI>The return type of <tt>x + y</tt> is convertible to <tt>InputIterator</tt>'s value type.<LI><tt>InputIterator</tt>'s value type is convertible to a type in <tt>OutputIterator</tt>'s set of value types.</UL>For the second version:<UL><LI><tt>InputIterator</tt> is a model of <A href="InputIterator.html">Input Iterator</A>.<LI><tt>OutputIterator</tt> is a model of <A href="OutputIterator.html">Output Iterator</A>.<LI><tt>BinaryFunction</tt> is a model of <A href="BinaryFunction.html">BinaryFunction</A>.<LI><tt>InputIterator</tt>'s value type is convertible to <tt>BinaryFunction</tt>'s first argument type and second argument type.<LI><tt>BinaryFunction</tt>'s result type is convertible to <tt>InputIterator</tt>'s value type.<LI><tt>InputIterator</tt>'s value type is convertible to a type in <tt>OutputIterator</tt>'s set of value types.</UL><h3>Preconditions</h3><UL><LI><tt>[first, last)</tt> is a valid range.<LI><tt>[result, result + (last - first))</tt> is a valid range.</UL><h3>Complexity</h3>Linear. Zero applications of the binary operation if <tt>[first, last)</tt>is a empty range, otherwise exactly <tt>(last - first) - 1</tt> applications.<h3>Example</h3><pre>int main(){ const int N = 10; int A[N]; fill(A, A+N, 1); cout << "A: "; <A href="copy.html">copy</A>(A, A+N, <A href="ostream_iterator.html">ostream_iterator</A><int>(cout, " ")); cout << endl; cout << "Partial sums of A: "; <A href="partial_sum.html">partial_sum</A>(A, A+N, <A href="ostream_iterator.html">ostream_iterator</A><int>(cout, " ")); cout << endl;} </pre><h3>Notes</h3><P><A name="1">[1]</A>Note that <tt>result</tt> is permitted to be the same iterator as<tt>first</tt>. This is useful for computing partial sums "in place".<P><A name="2">[2]</A>The binary operation is not required to be either associative orcommutative: the order of all operations is specified.<h3>See also</h3><tt><A href="adjacent_difference.html">adjacent_difference</A></tt>, <tt><A href="accumulate.html">accumulate</A></tt>, <tt><A href="inner_product.html">inner_product</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 © 1999 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> ?? 快捷鍵說明
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