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142 lines
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<HTML>
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<HEAD>
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<TITLE>ptr_fun()</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="priority-queue.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="push-heap.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>ptr_fun()</H2>
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<P><B>Library:</B> <A HREF="2-4.html">General utilities</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">Example</A></LI>
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<LI><A HREF="#sec6">See Also</A></LI>
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<LI><A HREF="#sec7">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>A function adaptor that creates a function object from a pointer to a function </P>
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<A NAME="sec3"><H3>Synopsis</H3></A>
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<PRE>#include <functional>
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namespace std {
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template<class Arg, class Result>
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pointer_to_unary_function<Arg, Result>
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ptr_fun(Result (*f)(Arg));
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template<class Arg1, class Arg2, class Result>
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pointer_to_binary_function<Arg1, Arg2, Result>
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ptr_fun(Result (*x)(Arg1, Arg2));
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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 <B><I><A HREF="pointer-to-unary-function.html">pointer_to_unary_function</A></I></B> and <B><I><A HREF="pointer-to-binary-function.html">pointer_to_binary_function</A></I></B> classes encapsulate pointers to functions, and use <SAMP>operator()</SAMP> so that the resulting object serves as a function object for the function.</P>
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<P>The <SAMP>ptr_fun()</SAMP> function is overloaded to create instances of <B><I><A HREF="pointer-to-unary-function.html">pointer_to_unary_function</A></I></B> or <B><I><A HREF="pointer-to-binary-function.html">pointer_to_binary_function</A></I></B> when included with the appropriate pointer to a function. </P>
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<A NAME="sec5"><H3>Example</H3></A>
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<UL><PRE>//
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// pnt2fnct.cpp
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//
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#include <algorithm> // for copy, transform
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#include <functional> // for ptr_fun
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#include <iostream> // cout, endl
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#include <iterator> // for ostream_iterator
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#include <deque> // for deque
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#include <vector> // for vector
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int factorial (int x)
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{
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return x > 1 ? x * factorial (x - 1) : x;
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}
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int main ()
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{
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typedef std::deque<int, std::allocator<int> > Deque;
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typedef std::vector<int, std::allocator<int> > Vector;
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typedef std::ostream_iterator<int, char,
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std::char_traits<char> >
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Iter;
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// Initialize a deque with an array of integers.
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const Deque::value_type a[] = { 1, 2, 3, 4, 5, 6, 7 };
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Deque d (a + 0, a + sizeof a / sizeof *a);
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// Create an empty vector to store the factorials.
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Vector v (Vector::size_type (7));
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// Compute factorials of the contents of 'd' and
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// store results in 'v'.
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std::transform (d.begin (), d.end (), v.begin (),
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std::ptr_fun (factorial));
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// Print the results.
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std::cout << "The following numbers: \n ";
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std::copy (d.begin (), d.end (), Iter (std::cout," "));
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std::cout << "\n\nHave the factorials: \n ";
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std::copy (v.begin (), v.end (), Iter (std::cout, " "));
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std::cout << std::endl;
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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>The following numbers:
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1 2 3 4 5 6 7
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Have the factorials:
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1 2 6 24 120 720 5040
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</PRE></UL>
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<A NAME="sec6"><H3>See Also</H3></A>
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<P><A HREF="functionobjects.html">Function Objects</A>, <B><I><A HREF="pointer-to-binary-function.html">pointer_to_binary_function</A></I></B>, <B><I><A HREF="pointer-to-unary-function.html">pointer_to_unary_function</A></I></B>, <B><I><A HREF="mem-fun.html">mem_fun</A></I></B></P>
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<A NAME="sec7"><H3>Standards Conformance</H3></A>
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<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 20.3.7</I></P>
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<BR>
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