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138 lines
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<HTML>
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<HEAD>
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<TITLE>for_each()</TITLE>
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<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
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<BODY BGCOLOR=#FFFFFF>
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<A HREF="find-if.html"><IMG SRC="images/bprev.gif" WIDTH=20 HEIGHT=21 ALT="Previous file" BORDER=O></A><A HREF="noframes.html"><IMG SRC="images/btop.gif" WIDTH=56 HEIGHT=21 ALT="Top of Document" BORDER=O></A><A HREF="booktoc.html"><IMG SRC="images/btoc.gif" WIDTH=56 HEIGHT=21 ALT="Contents" BORDER=O></A><A HREF="tindex.html"><IMG SRC="images/bindex.gif" WIDTH=56 HEIGHT=21 ALT="Index page" BORDER=O></A><A HREF="forwarditerators.html"><IMG SRC="images/bnext.gif" WIDTH=25 HEIGHT=21 ALT="Next file" BORDER=O></A><DIV CLASS="DOCUMENTNAME"><B>Apache C++ Standard Library Reference Guide</B></DIV>
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<H2>for_each()</H2>
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<P><B>Library:</B> <A HREF="2-9.html">Algorithms</A></P>
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<PRE><HR><B><I>Function</I></B><HR></PRE>
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<UL>
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<LI><A HREF="#sec1">Local Index</A></LI>
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<LI><A HREF="#sec2">Summary</A></LI>
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<LI><A HREF="#sec3">Synopsis</A></LI>
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<LI><A HREF="#sec4">Description</A></LI>
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<LI><A HREF="#sec5">Complexity</A></LI>
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<LI><A HREF="#sec6">Example</A></LI>
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<LI><A HREF="#sec7">See Also</A></LI>
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<LI><A HREF="#sec8">Standards Conformance</A></LI>
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</UL>
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<A NAME="sec1"><H3>Local Index</H3></A>
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No Entries
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<A NAME="sec2"><H3>Summary</H3></A>
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<P>Algorithm that applies a function to each element in a range</P>
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<A NAME="sec3"><H3>Synopsis</H3></A>
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<PRE>#include <algorithm>
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namespace std {
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template <class InputIterator, class Function>
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void Function for_each(InputIterator start,
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InputIterator finish,
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Function f);
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}
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</PRE>
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<A NAME="sec4"><H3>Description</H3></A>
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<P>The <SAMP>for_each()</SAMP> algorithm applies the function object <SAMP>f</SAMP> to each value in the range <SAMP>[start, finish)</SAMP>, where <SAMP>start</SAMP> and <SAMP>finish</SAMP> are iterators that define the sequence. Since this a non-mutating algorithm, the function <SAMP>f</SAMP> cannot make any modifications to the sequence, but it can achieve results through side effects (such as copying or printing). If <SAMP>f</SAMP> returns a result, the result is ignored.</P>
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<P><SAMP>for_each()</SAMP> returns the function object <SAMP>f</SAMP>.</P>
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<A NAME="sec5"><H3>Complexity</H3></A>
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<P>The function object <SAMP>f</SAMP> is applied exactly <SAMP>finish - start</SAMP> times.</P>
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<A NAME="sec6"><H3>Example</H3></A>
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<UL><PRE>//
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// for_each.cpp
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//
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#include <algorithm> // for for_each
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#include <functional> // for less, unary_function
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#include <iostream> // for cout, endl
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#include <set> // for set
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// Function object that outputs its argument times x.
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template <class Arg>
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class out_times_x: public std::unary_function<Arg, void>
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{
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Arg multiplier;
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public:
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out_times_x(const Arg &x) : multiplier (x) { }
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void operator()(const Arg &x) const {
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std::cout << x * multiplier << " " << std::endl;
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}
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};
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int main ()
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{
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// Typedef for convenience.
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typedef std::set<int, std::less<int>,
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std::allocator<int> > sequence;
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sequence::value_type arr [] = { 1, 2, 3, 4, 5 };
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// Populate a sequence from arr.
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sequence s(arr, arr + sizeof arr / sizeof *arr);
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// Construct a function object.
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out_times_x<sequence::value_type> f2(2);
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// Apply function object's operator() to each element.
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std::for_each(s.begin(), s.end(), f2);
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return 0;
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}
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Program Output
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</PRE></UL>
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<UL><PRE>2
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4
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6
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8
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10
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</PRE></UL>
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<A NAME="sec7"><H3>See Also</H3></A>
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<P><A HREF="algorithms.html">Algorithms</A>, <A HREF="functionobjects.html">Function Objects</A></P>
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<A NAME="sec8"><H3>Standards Conformance</H3></A>
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<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.1.1</I></P>
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