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| <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> <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&=()</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="#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 <valarray> |
| |
| namespace std { |
| template <class T> |
| 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<bool></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<bool></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 <class T> class mask_array { |
| public: |
| |
| // types |
| typedef T value_type; |
| |
| // destructor |
| ~mask_array(); |
| |
| // public assignment |
| void operator=(const valarray<T>& array) const; |
| // computed assignment |
| void operator*=(const valarray<T>& array) const; |
| void operator/=(const valarray<T>& array) const; |
| void operator%=(const valarray<T>& array) const; |
| void operator+=(const valarray<T>& array) const; |
| void operator-=(const valarray<T>& array) const; |
| void operator^=(const valarray<T>& array) const; |
| void operator&=(const valarray<T>& array) const; |
| void operator|=(const valarray<T>& array) const; |
| void operator<<=(const valarray<T>& array) const; |
| void operator>>=(const valarray<T>& array) const; |
| |
| // other |
| void operator=(const T&) const; |
| |
| private: |
| // constructors |
| mask_array(); |
| mask_array(const mask_array<T>&); |
| // operator= |
| mask_array<T>& operator=(const mask_array<T>& 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&);</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<T>& 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<T>& |
| <B>operator=</B>(const mask_array<T>& 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<T>& val) const; |
| void <B>operator/=</B>(const valarray<T>& val) const; |
| void <B>operator%=</B>(const valarray<T>& val) const; |
| void <B>operator+=</B>(const valarray<T>& val) const; |
| void <B>operator-=</B>(const valarray<T>& val) const; |
| void <B>operator^=</B>(const valarray<T>& val) const; |
| void <B>operator&=</B>(const valarray<T>& val) const; |
| void <B>operator|</B><B>=</B>(const valarray<T>& val) const; |
| void <B>operator<<=</B>(const valarray<T>& val) const; |
| void <B>operator>>=</B>(const valarray<T>& 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& 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 <valarray.h> // Includes valarray and |
| // provides stream inserter. |
| |
| typedef std::valarray<int> valarray_t; |
| typedef std::valarray<bool> 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<int>. |
| std::cout << "original valarray<int> vi\n\n" << vi << "\n\n"; |
| |
| // Print out the valarray<bool>. |
| std::cout << "original valarray<bool> mask\n\n" << mask |
| << "\n\n"; |
| |
| // Print a mask array. |
| std::cout << "vi[mask]\n\n" << vi[mask] << "\n\n"; |
| |
| // Double the values of the masked array and print out. |
| vi[mask] += static_cast<valarray_t> (vi[mask]); |
| std::cout << "vi[mask] += vi[mask]\n\n" << vi << std::endl; |
| |
| return 0; |
| } |
| |
| |
| Program Output: |
| </PRE></UL> |
| <UL><PRE>original valarray<int> vi |
| |
| [0,1,2,3,4,5,6,7,8,9] |
| |
| original valarray<bool> 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> |
| |
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