<!--
    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>mask_array</TITLE>
<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
<BODY BGCOLOR=#FFFFFF>
<A HREF="map.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="max.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>mask_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">Member Function</A></LI>
<LI><A HREF="#sec10">Example</A></LI>
<LI><A HREF="#sec11">See Also</A></LI>
<LI><A HREF="#sec12">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="#idx878">mask_array()</A><BR>
<A HREF="#idx881">operator%=()</A><BR>
<A HREF="#idx881">operator&amp;=()</A><BR>
</TD>
<TD VALIGN=top><A HREF="#idx881">operator&gt;&gt;=()</A><BR>
<A HREF="#idx881">operator&lt;&lt;=()</A><BR>
<A HREF="#idx881">operator*=()</A><BR>
</TD>
<TD VALIGN=top><A HREF="#idx881">operator+=()</A><BR>
<A HREF="#idx881">operator-=()</A><BR>
<A HREF="#idx881">operator/=()</A><BR>
</TD>
<TD VALIGN=top><A HREF="#idx879">operator=()</A><BR>
<A HREF="#idx881">operator^=()</A><BR>
<A HREF="#idx881">operator|</A><BR>
</TD></TR>
</TABLE></UL>

<A NAME="sec2"><H3>Summary</H3></A>
<P>A numeric array class that gives a masked view of 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 mask_array;
}
</PRE>
<A NAME="sec4"><H3>Description</H3></A>
<P><B><I>mask_array</I></B> gives a masked view into a <B><I><A HREF="valarray.html">valarray</A></I></B>.  A <B><I>mask_array</I></B> can only be produced by applying the mask subscript operator to a <B><I>valarray</I></B>. This subscript operator takes a <B><I>valarray&lt;bool&gt;</I></B> argument and produces a <B><I>mask_array</I></B>. Only the elements in the <B><I>valarray</I></B> whose corresponding elements in the <B><I>valarray&lt;bool&gt;</I></B> argument were <SAMP>true</SAMP> are selected by the <B><I>mask_array</I></B>. The elements in a <B><I>mask_array</I></B> are references to selected elements in the <B><I>valarray</I></B> (so changing an element in the <B><I>mask_array</I></B> really changes the corresponding element in the <B><I>valarray</I></B>). A <B><I>mask_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 a <B><I>mask_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 mask_array {
  public:

    // types
    typedef T value_type;

    // destructor
    ~mask_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;
 
    // other
    void operator=(const T&amp;) const; 

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

<A NAME="idx878"></A><PRE><B>mask_array</B>();
<B>mask_array</B>(const mask_array&amp;);</PRE>
<UL>
<P>All <B><I>mask_array</I></B> constructors are private and cannot be called directly. This prevents copy construction of <B><I>mask_array</I></B>s.</P>
</UL>

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

<A NAME="idx879"></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 a <B><I>mask_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="idx880"></A><PRE>mask_array&lt;T&gt;&amp; 
<B>operator=</B>(const mask_array&lt;T&gt;&amp; x);</PRE>
<UL>
<P>Private assignment operator. Cannot be called directly, thus preventing assignment between <B><I>mask_array</I></B>s.</P>
</UL>

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

<A NAME="idx881"></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><B>=</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 a <B><I>mask_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>Member Function</H3></A>

<A NAME="idx882"></A><PRE>void <B>operator=</B>(const T&amp; x) const;</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="sec10"><H3>Example</H3></A>

<UL><PRE>//
//  mask_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;bool&gt;   maskarray_t;

int main(void) {

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

  // Create a valarray of bools for a mask.
  maskarray_t::value_type  mbuf[10] = {1,0,1,1,1,0,0,1,1,0};
  maskarray_t              mask(mbuf,10);

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

  // Print out the valarray&lt;bool&gt;.
  std::cout &lt;&lt; "original valarray&lt;bool&gt; mask\n\n" &lt;&lt; mask 
            &lt;&lt; "\n\n";
  
  // Print a mask array.
  std::cout &lt;&lt; "vi[mask]\n\n" &lt;&lt; vi[mask] &lt;&lt; "\n\n";
  
  // Double the values of the masked array and print out.
  vi[mask] += static_cast&lt;valarray_t&gt; (vi[mask]);
  std::cout &lt;&lt; "vi[mask] += vi[mask]\n\n" &lt;&lt; vi &lt;&lt; std::endl;

  return 0;
}


Program Output:
</PRE></UL>
<UL><PRE>original valarray&lt;int&gt; vi

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

original valarray&lt;bool&gt; mask

[1,0,1,1,1,0,0,1,1,0]

vi[mask]

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

vi[mask] += vi[mask]

[0,1,4,6,8,5,6,14,16,9]
</PRE></UL>
<A NAME="sec11"><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="indirect-array.html">indirect_array</A></I></B></P>
<A NAME="sec12"><H3>Standards Conformance</H3></A>
<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 26.3.8</I></P>

<BR>
<HR>
<A HREF="map.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="max.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>