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| <TITLE>indirect_array</TITLE> |
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| <H2>indirect_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">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&=()</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="#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 <valarray> |
| |
| namespace std { |
| template <class T> |
| 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 <class T> class indirect_array { |
| public: |
| |
| // types |
| typedef T value_type; |
| |
| // destructor |
| ~indirect_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; |
| |
| // fill function |
| void operator=(const T&); |
| |
| private: |
| // constructors |
| indirect_array(); |
| indirect_array(const indirect_array<T>&); |
| |
| // operator = |
| indirect_array<T>& |
| operator=(const indirect_array<T>& 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&);</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<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 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<T>& |
| <B>operator=</B>(const indirect-_array<T>& 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& 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<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>(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 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 <valarray.h> // Includes valarray and |
| // provides stream inserter. |
| |
| typedef std::valarray<int> valarray_t; |
| typedef std::valarray<size_t> 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<int>. |
| std::cout << "original valarray vi\n\n" << vi << "\n\n"; |
| |
| // Print out the selective array. |
| std::cout << "vi[0,2,3,4,7,8]\n\n" << vi[selector] << "\n\n"; |
| |
| // Double the selected values. |
| vi[selector] += vi[selector]; |
| |
| // Print out the modified valarray. |
| std::cout << "vi[0,2,3,4,7,8] += vi[0,2,3,4,7,8]\n\n" << vi |
| << 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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