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| <H2>gslice</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">Accessors</A></LI> |
| <LI><A HREF="#sec8">Example</A></LI> |
| <LI><A HREF="#sec9">See Also</A></LI> |
| <LI><A HREF="#sec10">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="#idx647">gslice()</A><BR> |
| </TD> |
| <TD VALIGN=top><A HREF="#idx651">size()</A><BR> |
| </TD> |
| <TD VALIGN=top><A HREF="#idx650">start()</A><BR> |
| </TD> |
| <TD VALIGN=top><A HREF="#idx652">stride()</A><BR> |
| </TD></TR> |
| </TABLE></UL> |
| |
| <A NAME="sec2"><H3>Summary</H3></A> |
| <P>A numeric array class used to represent a generalized slice from an array</P> |
| <A NAME="sec3"><H3>Synopsis</H3></A> |
| |
| <PRE>#include <valarray> |
| |
| namespace std { |
| class gslice; |
| } |
| </PRE> |
| <A NAME="sec4"><H3>Description</H3></A> |
| <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> |
| <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> |
| <A NAME="sec5"><H3>Interface</H3></A> |
| |
| <UL><PRE>namespace std{ |
| |
| class gslice { |
| public: |
| // constructors |
| gslice(); |
| gslice(size_t, const valarray<size_t>&, |
| const valarray<size_t>&); |
| gslice(const gslice&); |
| |
| // Accessors |
| size_t start() const; |
| valarray<size_t> size() const; |
| valarray<size_t> stride() const; |
| }; |
| } |
| </PRE></UL> |
| <A NAME="sec6"><H3>Constructors</H3></A> |
| |
| <A NAME="idx647"></A><PRE><B>gslice</B>();</PRE> |
| <UL> |
| <P>Default constructor creates a <B><I>gslice</I></B> specifying no elements. </P> |
| </UL> |
| |
| |
| <A NAME="idx648"></A><PRE><B>gslice</B>(size_t start, const valarray<size_t>& length, |
| const valarray<size_t>& stride);</PRE> |
| <UL> |
| <P>Creates a <B><I>gslice</I></B> with starting index, length, and stride as indicated by the arguments. </P> |
| </UL> |
| |
| |
| <A NAME="idx649"></A><PRE><B>gslice</B>(const gslice&)</PRE> |
| <UL> |
| <P>Creates a <B><I>gslice</I></B> with starting index, length, and stride as indicated by the slice argument. </P> |
| </UL> |
| |
| <A NAME="sec7"><H3>Accessors</H3></A> |
| |
| <A NAME="idx650"></A><PRE>size_t <B>start</B>() const;</PRE> |
| <UL> |
| <P>Returns the starting index of the <B><I>gslice</I></B>.</P> |
| </UL> |
| |
| |
| <A NAME="idx651"></A><PRE>valarray<size_t> <B>size</B>() const;</PRE> |
| <UL> |
| <P>Returns a <SAMP>valarray<size_t></SAMP> containing the lengths of the <B><I>gslice</I></B>.</P> |
| </UL> |
| |
| |
| <A NAME="idx652"></A><PRE>valarray<size_t> <B>stride</B>() const;</PRE> |
| <UL> |
| <P>Returns a <SAMP>valarray<size_t></SAMP> containing the strides of the <B><I>gslice</I></B>. </P> |
| </UL> |
| |
| <A NAME="sec8"><H3>Example</H3></A> |
| |
| <UL><PRE>// |
| // gslice.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 ints. |
| valarray_t::value_type ibuf[27] = |
| { 0, 1, 2, 3, 4, 5, 6, 7, 8, |
| 9, 10, 11, 12, 13, 14, 15, 16, 17, |
| 18, 19, 20, 21, 22, 23, 24, 25, 26 }; |
| valarray_t vi(ibuf, 27); |
| |
| // Create length and stride valarray |
| selector_t::value_type length_buf[3] = {3,3,3}; |
| selector_t::value_type stride_buf[3] = {9,3,1}; |
| selector_t length_val(length_buf, 3); |
| selector_t stride_val(stride_buf, 3); |
| |
| // Print out the valarray<int>. |
| std::cout << "original valarray vi\n\n" << vi << "\n\n"; |
| |
| // Print out all three dimensions (the entire valarray). |
| std::cout << "vi[gslice(0,{3,3,3},{9,3,1})]\n\n" |
| << vi[std::gslice(0,length_val,stride_val)] |
| << "\n\n"; |
| |
| // Print a two dimensional slice out of the middle. |
| selector_t::value_type length_buf2[] = {3, 3}; |
| selector_t::value_type stride_buf2[] = {3, 1}; |
| selector_t length_val2(length_buf2, 2); |
| selector_t stride_val2(stride_buf2, 2); |
| |
| std::cout << "vi[gslice(9,{3,3},{3,1})]\n\n" |
| << vi[std::gslice(9,length_val2,stride_val2)] |
| << "\n\n"; |
| |
| // Print another two dimensional slice out of the middle but |
| // orthogonal to one we just did. |
| stride_val2[0] = 9; |
| stride_val2[1] = 1; |
| |
| std::cout << "vi[gslice(3,{3,3},{9,1})]\n\n" |
| << vi[std::gslice(3,length_val2,stride_val2)] |
| << "\n\n"; |
| |
| // Print out the last plane in the middle -- orthogonal to |
| // both of the previous ones. |
| stride_val2[0] = 3; |
| stride_val2[1] = 9; |
| |
| std::cout << "vi[gslice(1,{3,3},{3,9})]\n\n" |
| << vi[std::gslice(1,length_val2,stride_val2)] |
| << "\n\n"; |
| |
| // Now how about a diagonal slice, upper left front to lower right |
| // back. |
| stride_val2[0] = 3; |
| stride_val2[1] = 10; |
| |
| std::cout << "vi[gslice(0,{3,3},{3,10})]\n\n" |
| << vi[std::gslice(0,length_val2,stride_val2)] |
| << "\n\n"; |
| |
| return 0; |
| } |
| |
| |
| Program Output: |
| original valarray vi |
| |
| [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22, |
| 23,24,25,26] |
| |
| vi[gslice(0,{3,3,3},{9,3,1})] |
| |
| [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22, |
| 23,24,25,26] |
| |
| vi[gslice(9,{3,3},{3,1})] |
| |
| [9,10,11,12,13,14,15,16,17] |
| |
| vi[gslice(3,{3,3},{9,1})] |
| |
| [3,4,5,12,13,14,21,22,23] |
| |
| vi[gslice(1,{3,3},{3,9})] |
| |
| [1,10,19,4,13,22,7,16,25] |
| |
| vi[gslice(0,{3,3},{3,10})] |
| |
| [0,10,20,3,13,23,6,16,26] |
| |
| </PRE></UL> |
| <UL><PRE></PRE></UL> |
| <A NAME="sec9"><H3>See Also</H3></A> |
| <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> |
| <A NAME="sec10"><H3>Standards Conformance</H3></A> |
| <P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 26.3.6</I></P> |
| |
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