<!--
    Licensed to the Apache Software  Foundation (ASF) under one or more
    contributor  license agreements.  See  the NOTICE  file distributed
    with  this  work  for  additional information  regarding  copyright
    ownership.   The ASF  licenses this  file to  you under  the Apache
    License, Version  2.0 (the  License); you may  not use  this file
    except in  compliance with the License.   You may obtain  a copy of
    the License at

    http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the  License is distributed on an  "AS IS" BASIS,
    WITHOUT  WARRANTIES OR CONDITIONS  OF ANY  KIND, either  express or
    implied.   See  the License  for  the  specific language  governing
    permissions and limitations under the License.

    Copyright 1999-2007 Rogue Wave Software, Inc.
-->

<HTML>
<HEAD>
<TITLE>generate(), generate_n()</TITLE>
<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
<BODY BGCOLOR=#FFFFFF>
<A HREF="functional-h.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="get-temporary-buffer.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>
<H2>generate(), generate_n()</H2>
<P><B>Library:</B>&nbsp;&nbsp;<A HREF="2-9.html">Algorithms</A></P>

<PRE><HR><B><I>Function</I></B><HR></PRE>

<UL>
<LI><A HREF="#sec1">Local Index</A></LI>
<LI><A HREF="#sec2">Summary</A></LI>
<LI><A HREF="#sec3">Synopsis</A></LI>
<LI><A HREF="#sec4">Description</A></LI>
<LI><A HREF="#sec5">Complexity</A></LI>
<LI><A HREF="#sec6">Example</A></LI>
<LI><A HREF="#sec7">See Also</A></LI>
<LI><A HREF="#sec8">Standards Conformance</A></LI>
</UL>
<A NAME="sec1"><H3>Local Index</H3></A>
No Entries
<A NAME="sec2"><H3>Summary</H3></A>
<P>Algorithm that assigns each element in a range a value produced by repeated application of the given function object</P>
<A NAME="sec3"><H3>Synopsis</H3></A>

<PRE>#include &lt;algorithm&gt;

namespace std {
  template &lt;class ForwardIterator, class Generator&gt;
  void generate(ForwardIterator start, ForwardIterator finish,
                Generator gen);

  template &lt;class OutputIterator, class Size, class Generator&gt;
  void generate_n(OutputIterator start, Size n,
                  Generator gen);
}
</PRE>
<A NAME="sec4"><H3>Description</H3></A>
<P>A value-generator function returns a value each time it is invoked. The algorithms <SAMP>generate()</SAMP> and <SAMP><A HREF="generate.html">generate_n()</A></SAMP> assign each element in the sequence <SAMP>[start, finish)</SAMP> or <SAMP>[start, start + n) </SAMP>the return value of the generator function <SAMP>gen()</SAMP>. The function <SAMP>gen()</SAMP> takes no arguments. (<SAMP>gen()</SAMP> can be a function or a class with an <SAMP>operator()</SAMP> defined that takes no arguments.)</P>
<P><SAMP><A HREF="generate.html">generate_n()</A></SAMP> assumes that all iterators in the range <SAMP>[start, start + n]</SAMP> are dereferenceable, unless <SAMP>start</SAMP> is an insert iterator.</P>
<A NAME="sec5"><H3>Complexity</H3></A>
<P>The <SAMP>generate()</SAMP> and <SAMP><A HREF="generate.html">generate_n()</A></SAMP> algorithms invoke <SAMP>gen()</SAMP> and assign its return value exactly <SAMP>finish - start</SAMP> (or <SAMP>n</SAMP>) times.</P>
<A NAME="sec6"><H3>Example</H3></A>

<UL><PRE>//
// generate.cpp
//

#include &lt;algorithm&gt;    // for generate, generate_n
#include &lt;iostream&gt;     // for cout, endl
#include &lt;vector&gt;       // for vector


// Value generator simply doubles the current value 
// and returns it.
template &lt;class T&gt;
class generator
{
    T val_;
public:
    generator(const T &amp;val) : val_ (val) { }
    T operator()() {
        return val_ += val_;
    }
};


int main ()
{
    // Typedef for convenience.
    typedef std::vector&lt;short, 
                        std::allocator&lt;short&gt; &gt; vector;

    vector::value_type arr[4] = { 1, 2, 3, 4 };

    // Set up two vectors.
    vector v1(arr, arr + sizeof arr / sizeof *arr);
    vector v2 = v1;

    // Set up one empty vector.
    vector v3;

    // Create a generator function object.
    generator&lt;vector::value_type&gt; gen(1);

    // Generate values for all of v1.
    std::generate(v1.begin(), v1.end(), gen);

    // Generate values for first 3 of v2.
    std::generate_n(v2.begin(), 3, gen);

    // Use back_insert_iterator to generate 5 values for v3.
    std::generate_n(std::back_inserter(v3), 5, gen);

    // Copy all three to cout.
    std::ostream_iterator&lt;vector::value_type, char,
             std::char_traits&lt;char&gt; &gt; out(std::cout, " ");

    std::copy(v1.begin(), v1.end(), out);
    std::cout &lt;&lt; std::endl;

    std::copy(v2.begin(), v2.end(), out);
    std::cout &lt;&lt; std::endl;

    std::copy(v3.begin(), v3.end(), out);
    std::cout &lt;&lt; std::endl;

    // Generate 3 values into cout.
    std::generate_n(out, 3, gen);
    std::cout &lt;&lt; std::endl;

    return 0;
}


Program Output:
</PRE></UL>
<UL><PRE>2 4 8 16 
2 4 8 4 
2 4 8 16 32 
2 4 8 
</PRE></UL>
<A NAME="sec7"><H3>See Also</H3></A>
<P><A HREF="functionobjects.html">Function Objects</A></P>
<A NAME="sec8"><H3>Standards Conformance</H3></A>
<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.2.6</I></P>

<BR>
<HR>
<A HREF="functional-h.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="get-temporary-buffer.html"><IMG SRC="images/bnext.gif" WIDTH=20 HEIGHT=21 ALT="Next file" BORDER=O></A>

<!-- Google Analytics tracking code -->
<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
</script>
<script type="text/javascript">
    _uacct = "UA-1775151-1";
    urchinTracker();
</script>
<!-- end of Google Analytics tracking code -->

</BODY>
</HTML>