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<HTML>
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<HEAD>
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<TITLE>gslice</TITLE>
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<LINK REL=StyleSheet HREF="../rw.css" TYPE="text/css" TITLE="Apache stdcxx Stylesheet"></HEAD>
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<BODY BGCOLOR=#FFFFFF>
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<A HREF="greater-equal.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="gslice-array.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>
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<H2>gslice</H2>
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<P><B>Library:</B> <A HREF="2-10.html">Numerics</A></P>
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<PRE><HR><B><I>Does not inherit</I></B><HR></PRE>
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<UL>
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<LI><A HREF="#sec1">Local Index</A></LI>
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<LI><A HREF="#sec2">Summary</A></LI>
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<LI><A HREF="#sec3">Synopsis</A></LI>
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<LI><A HREF="#sec4">Description</A></LI>
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<LI><A HREF="#sec5">Interface</A></LI>
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<LI><A HREF="#sec6">Constructors</A></LI>
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<LI><A HREF="#sec7">Accessors</A></LI>
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<LI><A HREF="#sec8">Example</A></LI>
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<LI><A HREF="#sec9">See Also</A></LI>
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<LI><A HREF="#sec10">Standards Conformance</A></LI>
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</UL>
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<A NAME="sec1"><H3>Local Index</H3></A>
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<H4>Members</H4>
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<UL><TABLE CELLPADDING=3>
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<TR><TD VALIGN=top>
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<A HREF="#idx647">gslice()</A><BR>
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</TD>
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<TD VALIGN=top><A HREF="#idx651">size()</A><BR>
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</TD>
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<TD VALIGN=top><A HREF="#idx650">start()</A><BR>
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</TD>
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<TD VALIGN=top><A HREF="#idx652">stride()</A><BR>
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</TD></TR>
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</TABLE></UL>
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<A NAME="sec2"><H3>Summary</H3></A>
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<P>A numeric array class used to represent a generalized slice from an array</P>
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<A NAME="sec3"><H3>Synopsis</H3></A>
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<PRE>#include <valarray>
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namespace std {
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class gslice;
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}
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</PRE>
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<A NAME="sec4"><H3>Description</H3></A>
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<P><B><I>gslice</I></B> represents a generalized slice from an array. A generalized slice contains a starting index, a set of lengths, and a set of strides. The number of lengths and strides must be equal. Together the lengths and strides allow a slice from a multiple dimension array (with the dimension equal to the number of strides) to be represented on a one-dimensional <B><I><A HREF="valarray.html">valarray</A></I></B>. The <B><I>gslice</I></B> maps a set of <SAMP>n</SAMP> indices <SAMP>(ij)</SAMP>, where <SAMP>n</SAMP> is equal to the number of strides, to a single index <SAMP>k</SAMP>. </P>
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<P>When applied to a <B><I><A HREF="valarray.html">valarray</A></I></B> using the <B><I>gslice</I></B> subscript operator (see <B><I>valarray</I></B>), a <B><I>gslice</I></B> produces a <B><I><A HREF="gslice-array.html">gslice_array</A></I></B>. The <B><I>gslice_array</I></B> class creates a view into the original <B><I>valarray</I></B> that is tailored to match parameters of the <B><I>gslice</I></B>. The elements in a <B><I>gslice_array</I></B> are references to the elements in the original array. </P>
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<A NAME="sec5"><H3>Interface</H3></A>
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<UL><PRE>namespace std{
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class gslice {
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public:
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// constructors
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gslice();
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gslice(size_t, const valarray<size_t>&,
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const valarray<size_t>&);
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gslice(const gslice&);
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// Accessors
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size_t start() const;
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valarray<size_t> size() const;
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valarray<size_t> stride() const;
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};
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}
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</PRE></UL>
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<A NAME="sec6"><H3>Constructors</H3></A>
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<A NAME="idx647"></A><PRE><B>gslice</B>();</PRE>
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<UL>
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<P>Default constructor creates a <B><I>gslice</I></B> specifying no elements. </P>
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</UL>
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<A NAME="idx648"></A><PRE><B>gslice</B>(size_t start, const valarray<size_t>& length,
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const valarray<size_t>& stride);</PRE>
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<UL>
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<P>Creates a <B><I>gslice</I></B> with starting index, length, and stride as indicated by the arguments. </P>
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</UL>
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<A NAME="idx649"></A><PRE><B>gslice</B>(const gslice&)</PRE>
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<UL>
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<P>Creates a <B><I>gslice</I></B> with starting index, length, and stride as indicated by the slice argument. </P>
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</UL>
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<A NAME="sec7"><H3>Accessors</H3></A>
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<A NAME="idx650"></A><PRE>size_t <B>start</B>() const;</PRE>
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<UL>
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<P>Returns the starting index of the <B><I>gslice</I></B>.</P>
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</UL>
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<A NAME="idx651"></A><PRE>valarray<size_t> <B>size</B>() const;</PRE>
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<UL>
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<P>Returns a <SAMP>valarray<size_t></SAMP> containing the lengths of the <B><I>gslice</I></B>.</P>
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</UL>
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<A NAME="idx652"></A><PRE>valarray<size_t> <B>stride</B>() const;</PRE>
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<UL>
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<P>Returns a <SAMP>valarray<size_t></SAMP> containing the strides of the <B><I>gslice</I></B>. </P>
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</UL>
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<A NAME="sec8"><H3>Example</H3></A>
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<UL><PRE>//
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// gslice.cpp
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//
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#include <valarray.h> // Includes valarray and provides
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// stream inserter.
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typedef std::valarray<int> valarray_t;
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typedef std::valarray<size_t> selector_t;
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int main(void) {
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// Create a valarray of ints.
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valarray_t::value_type ibuf[27] =
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{ 0, 1, 2, 3, 4, 5, 6, 7, 8,
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9, 10, 11, 12, 13, 14, 15, 16, 17,
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18, 19, 20, 21, 22, 23, 24, 25, 26 };
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valarray_t vi(ibuf, 27);
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// Create length and stride valarray
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selector_t::value_type length_buf[3] = {3,3,3};
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selector_t::value_type stride_buf[3] = {9,3,1};
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selector_t length_val(length_buf, 3);
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selector_t stride_val(stride_buf, 3);
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// Print out the valarray<int>.
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std::cout << "original valarray vi\n\n" << vi << "\n\n";
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// Print out all three dimensions (the entire valarray).
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std::cout << "vi[gslice(0,{3,3,3},{9,3,1})]\n\n"
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<< vi[std::gslice(0,length_val,stride_val)]
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<< "\n\n";
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// Print a two dimensional slice out of the middle.
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selector_t::value_type length_buf2[] = {3, 3};
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selector_t::value_type stride_buf2[] = {3, 1};
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selector_t length_val2(length_buf2, 2);
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selector_t stride_val2(stride_buf2, 2);
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std::cout << "vi[gslice(9,{3,3},{3,1})]\n\n"
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<< vi[std::gslice(9,length_val2,stride_val2)]
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<< "\n\n";
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// Print another two dimensional slice out of the middle but
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// orthogonal to one we just did.
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stride_val2[0] = 9;
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stride_val2[1] = 1;
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std::cout << "vi[gslice(3,{3,3},{9,1})]\n\n"
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<< vi[std::gslice(3,length_val2,stride_val2)]
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<< "\n\n";
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// Print out the last plane in the middle -- orthogonal to
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// both of the previous ones.
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stride_val2[0] = 3;
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stride_val2[1] = 9;
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std::cout << "vi[gslice(1,{3,3},{3,9})]\n\n"
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<< vi[std::gslice(1,length_val2,stride_val2)]
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<< "\n\n";
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// Now how about a diagonal slice, upper left front to lower right
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// back.
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stride_val2[0] = 3;
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stride_val2[1] = 10;
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std::cout << "vi[gslice(0,{3,3},{3,10})]\n\n"
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<< vi[std::gslice(0,length_val2,stride_val2)]
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<< "\n\n";
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return 0;
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}
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Program Output:
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original valarray vi
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[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,
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23,24,25,26]
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vi[gslice(0,{3,3,3},{9,3,1})]
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[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,
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23,24,25,26]
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vi[gslice(9,{3,3},{3,1})]
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[9,10,11,12,13,14,15,16,17]
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vi[gslice(3,{3,3},{9,1})]
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[3,4,5,12,13,14,21,22,23]
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vi[gslice(1,{3,3},{3,9})]
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[1,10,19,4,13,22,7,16,25]
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vi[gslice(0,{3,3},{3,10})]
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[0,10,20,3,13,23,6,16,26]
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</PRE></UL>
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<UL><PRE></PRE></UL>
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<A NAME="sec9"><H3>See Also</H3></A>
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<P><B><I><A HREF="valarray.html">valarray</A></I></B>, <B><I><A HREF="slice-array.html">slice_array</A></I></B>, <B><I><A HREF="slice.html">slice</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>, <B><I><A HREF="indirect-array.html">indirect_array</A></I></B></P>
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<A NAME="sec10"><H3>Standards Conformance</H3></A>
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<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 26.3.6</I></P>
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<BR>
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