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<A HREF="includes.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="inner-product.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>indirect_array</H2>
<P><B>Library:</B>&nbsp;&nbsp;<A HREF="2-10.html">Numerics</A></P>

<PRE><HR><B><I>Does not inherit</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">Interface</A></LI>
<LI><A HREF="#sec6">Constructors</A></LI>
<LI><A HREF="#sec7">Assignment Operators</A></LI>
<LI><A HREF="#sec8">Computed Assignment Operators</A></LI>
<LI><A HREF="#sec9">Example</A></LI>
<LI><A HREF="#sec10">See Also</A></LI>
<LI><A HREF="#sec11">Standards Conformance</A></LI>
</UL>
<A NAME="sec1"><H3>Local Index</H3></A>
<H4>Members</H4>
<UL><TABLE CELLPADDING=3>
<TR><TD VALIGN=top>
<A HREF="#idx658">indirect_array()</A><BR>
<A HREF="#idx662">operator%=()</A><BR>
<A HREF="#idx662">operator&amp;=()</A><BR>
</TD>
<TD VALIGN=top><A HREF="#idx662">operator&gt;&gt;=()</A><BR>
<A HREF="#idx662">operator&lt;&lt;=()</A><BR>
<A HREF="#idx662">operator*=()</A><BR>
</TD>
<TD VALIGN=top><A HREF="#idx662">operator+=()</A><BR>
<A HREF="#idx662">operator-=()</A><BR>
<A HREF="#idx662">operator/=()</A><BR>
</TD>
<TD VALIGN=top><A HREF="#idx659">operator=()</A><BR>
<A HREF="#idx662">operator^=()</A><BR>
<A HREF="#idx662">operator|=()</A><BR>
</TD></TR>
</TABLE></UL>

<A NAME="sec2"><H3>Summary</H3></A>
<P>A numeric array class used to represent elements selected from a <B><I><A HREF="valarray.html">valarray</A></I></B></P>
<A NAME="sec3"><H3>Synopsis</H3></A>

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

namespace std {
  template &lt;class T&gt;
  class indirect_array;
}
</PRE>
<A NAME="sec4"><H3>Description</H3></A>
<P><B><I>indirect_array</I></B> creates a selective view into a <B><I><A HREF="valarray.html">valarray</A></I></B>. An <B><I>indirect_array</I></B> is produced by applying the indirect subscript operator to a <B><I>valarray</I></B>. The indirect array produced by this subscript contains only the elements of the <B><I>valarray</I></B> whose indices appear as values in the argument. The elements in an <B><I>indirect_array</I></B> are references to selected elements in the <B><I>valarray</I></B>. For this reason, changing an element in the <B><I>indirect_array</I></B> really changes the corresponding element in the <B><I>valarray</I></B>. An <B><I>indirect_array</I></B> does not itself hold any distinct elements. The template cannot be instantiated directly since all its constructors are private. However, you can copy an <B><I>indirect_array</I></B> to a <B><I>valarray</I></B> using either the <B><I>valarray</I></B> copy constructor or the assignment operator. Reference semantics are lost at that point. </P>
<A NAME="sec5"><H3>Interface</H3></A>

<UL><PRE>namespace std{ 

  template &lt;class T&gt; class indirect_array {
  public:

    // types
    typedef T value_type;

    // destructor
    ~indirect_array();

    // public assignment
    void operator=(const valarray&lt;T&gt;&amp; array) const;
  
    // computed assignment
    void operator*=(const valarray&lt;T&gt;&amp; array) const;
    void operator/=(const valarray&lt;T&gt;&amp; array) const;
    void operator%=(const valarray&lt;T&gt;&amp; array) const;
    void operator+=(const valarray&lt;T&gt;&amp; array) const;
    void operator-=(const valarray&lt;T&gt;&amp; array) const;
    void operator^=(const valarray&lt;T&gt;&amp; array) const;
    void operator&amp;=(const valarray&lt;T&gt;&amp; array) const;
    void operator|=(const valarray&lt;T&gt;&amp; array) const;
    void operator&lt;&lt;=(const valarray&lt;T&gt;&amp; array) const;
    void operator&gt;&gt;=(const valarray&lt;T&gt;&amp; array) const;
 
    // fill function
    void operator=(const T&amp;);  

  private:
    // constructors
    indirect_array();
    indirect_array(const indirect_array&lt;T&gt;&amp;);
  
    // operator = 
    indirect_array&lt;T&gt;&amp; 
       operator=(const indirect_array&lt;T&gt;&amp; array);
  };
}
</PRE></UL>
<A NAME="sec6"><H3>Constructors</H3></A>

<A NAME="idx658"></A><PRE><B>indirect_array</B>();
<B>indirect_array</B>(const indirect_array&amp;);</PRE>
<UL>
<P>All <B><I>indirect_array</I></B> constructors are private and cannot be called directly. This prevents copy construction of <B><I>indirect_arrays</I></B>.</P>
</UL>

<A NAME="sec7"><H3>Assignment Operators</H3></A>

<A NAME="idx659"></A><PRE>void <B>operator=</B>(const valarray&lt;T&gt;&amp; x) const;</PRE>
<UL>
<P>Assigns values from <SAMP>x </SAMP>to the selected elements of the <B><I><A HREF="valarray.html">valarray</A></I></B> that self refers to. Remember that an <B><I>indirect_array</I></B> never holds any elements itself; it simply refers to selected elements in the <B><I>valarray</I></B> used to generate it.</P>
</UL>


<A NAME="idx660"></A><PRE>indirect_array&lt;T&gt;&amp; 
<B>operator=</B>(const indirect-_array&lt;T&gt;&amp; x);</PRE>
<UL>
<P>Private assignment operator. Cannot be called directly, thus preventing assignment between <B><I>indirect_arrays</I></B>.</P>
</UL>


<A NAME="idx661"></A><PRE>void <B>operator=</B>(const T&amp; x);</PRE>
<UL>
<P>Assigns <SAMP>x</SAMP> to the selected elements of the <B><I><A HREF="valarray.html">valarray</A></I></B> that self refers to. </P>
</UL>

<A NAME="sec8"><H3>Computed Assignment Operators</H3></A>

<A NAME="idx662"></A><PRE>void <B>operator*=</B>(const valarray&lt;T&gt;&amp; val) const;
void <B>operator/=</B>(const valarray&lt;T&gt;&amp; val) const;
void <B>operator%=</B>(const valarray&lt;T&gt;&amp; val) const;
void <B>operator+=</B>(const valarray&lt;T&gt;&amp; val) const;
void <B>operator-=</B>(const valarray&lt;T&gt;&amp; val) const;
void <B>operator^=</B>(const valarray&lt;T&gt;&amp; val) const;
void <B>operator&amp;=</B>(const valarray&lt;T&gt;&amp; val) const;
void <B>operator|=</B>(const valarray&lt;T&gt;&amp; val) const;
void <B>operator&lt;&lt;=</B>(const valarray&lt;T&gt;&amp; val) const;
void <B>operator&gt;&gt;=</B>(const valarray&lt;T&gt;&amp; val) const;</PRE>
<UL>
<P>Applies the indicated operation using elements from <SAMP>val</SAMP> to the selected elements of the <B><I><A HREF="valarray.html">valarray</A></I></B> that self refers to. Remember that an <B><I>indirect_array</I></B> never holds any elements itself; it simply refers to selected elements in the <B><I>valarray</I></B> used to generate it.</P>
</UL>

<A NAME="sec9"><H3>Example</H3></A>

<UL><PRE>//
//  indirect_array.cpp
//

#include &lt;valarray.h&gt;  // Includes valarray and 
                       // provides stream inserter.

typedef std::valarray&lt;int&gt;    valarray_t;
typedef std::valarray&lt;size_t&gt; selector_t;

int main(void) {

  // Create a valarray of integers.
  valarray_t::value_type vbuf[10] = {0,1,2,3,4,5,6,7,8,9};
  valarray_t vi(vbuf, (sizeof vbuf / sizeof *vbuf));

  // Create a valarray of indices for a selector.
  selector_t::value_type sbuf[6] = {0,2,3,4,7,8};
  selector_t selector(sbuf, (sizeof sbuf / sizeof *sbuf));

  // Print out the valarray&lt;int&gt;.
  std::cout &lt;&lt; "original valarray vi\n\n" &lt;&lt; vi &lt;&lt; "\n\n";

  // Print out the selective array.
  std::cout &lt;&lt; "vi[0,2,3,4,7,8]\n\n" &lt;&lt;  vi[selector] &lt;&lt; "\n\n";
  
  // Double the selected values.
  vi[selector] += vi[selector];

  // Print out the modified valarray.
  std::cout &lt;&lt; "vi[0,2,3,4,7,8] += vi[0,2,3,4,7,8]\n\n" &lt;&lt; vi 
            &lt;&lt; std::endl;

  return 0;
}


Program Output:
</PRE></UL>
<UL><PRE>original valarray vi

[0,1,2,3,4,5,6,7,8,9]

vi[0,2,3,4,7,8]

[0,2,3,4,7,8]

vi[0,2,3,4,7,8] += vi[0,2,3,4,7,8]

[0,1,4,6,8,5,6,14,16,9]
</PRE></UL>
<A NAME="sec10"><H3>See Also</H3></A>
<P><B><I><A HREF="slice.html">slice</A></I></B>, <B><I><A HREF="slice-array.html">slice_array</A></I></B>, <B><I><A HREF="valarray.html">valarray</A></I></B>, <B><I><A HREF="gslice.html">gslice</A></I></B>, <B><I><A HREF="gslice-array.html">gslice_array</A></I></B>, <B><I><A HREF="mask-array.html">mask_array</A></I></B></P>
<A NAME="sec11"><H3>Standards Conformance</H3></A>
<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 26.3.9</I></P>

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