.\" ident @(#)gslice.3
.\" Standard Template Library
.\" $$RW_INSERT_HEADER "slyrs.man"
.TH gslice 3C++ "02 Apr 1998" "Rogue Wave Software" "-"
.ce2
Standard C++ Library   
Copyright 1998, Rogue Wave Software, Inc.   

.SH NAME

\f2gslice\fP

\ - A numeric array class used to represent a generalized slice from an array.



.SH  SYNOPSIS


.br
#include <valarray>
.br
class gslice ;



.SH  DESCRIPTION


gslice_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 valarray. The gslice maps a set of \f2n\fP indices \f2(ij)\fP, where \f2n\fP is equal to the number of strides, to a single index \f2k\fP. 

When applied to a valarray using the gslice subscript operator (see valarray) a gslice produces a gslice_array. The gslice_array class creates a view into the original valarray that is tailored to match parameters of the gslice. The elements in a gslice_array are references to the elements in the original array. 



.SH  INTERFACE


.br
class gslice {
.br
public:
.RE
.RS 2
// constructors
.RE
.RS 1
gslice();
.br
gslice(size_t, const valarray<size_t>&, 
.RE
.RS 8
const valarray<size_t>&);
.RE
.RS 1
gslice (const gslice&);
.RE
.RS 0

.RE
.RS 2
// Accessors
.RE
.RS 1
size_t start() const;
.br
valarray<size_t> size() const;
.br
valarray<size_t> stride() const;
.RE
.RS 0
};



.SH  CONSTRUCTORS 



.br
gslice();
.RE
.RS 3


Default constructor creates a gslice specifying no elements. 

.RE


.br
gslice(size_t start, const valarray<size_t>& length,
.RE
.RS 6
const valarray<size_t>& stride);
.RE
.RS 3


Creates a slice with starting index, length and stride as indicated by the arguments. 

.RE


.RE
.RS 0
gslice(const gslice&)
.RE
.RS 3


Creates a slice with starting index, length and stride as indicated by the slice argument. 

.RE



.SH  ACCESSORS



.br
size_t start();
.RE
.RS 3


Returns the starting index of the gslice.

.RE


.br
valarraysize_t> size();
.RE
.RS 3


Returns a valarray<size_t> containing the lengths of the gslice.

.RE


.br
Valarray<size_t> stride();
.RE
.RS 3


Returns a valarray<size_t> containing the strides of the gslice. 

.RE



.SH  EXAMPLE



.br
//
.br
// gslice.cpp
.br
//
.br
#include "valarray.h" // Contains a valarray stream inserter
.br
using namespace std;
.br

.br
int main(void)
.br
{
.RE
.RS 1
int ibuf[27] = 
.RE
.RS 3
{0,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,9,2,3,4,5,6,7,8,9,10};
.RE
.RS 1
size_t len_buf[3] = {3,3,3};
.br
size_t stride_buf[3] = {9,3,1};
.RE
.RS 0

.RE
.RS 2
// create a valarray of ints
.RE
.RS 1
valarray<int>  vi(ibuf,27);
.RE
.RS 0

.RE
.RS 2
// create length and stride valarrays
.RE
.RS 1
valarray<size_t> len(len_buf,3);
.br
valarray<size_t> stride(stride_buf,3);
.RE
.RS 0

.RE
.RS 2
// print out the valarray
.RE
.RS 1
cout << vi << endl;
.RE
.RS 0

.RE
.RS 2
// Print out all three dimensions (the entire valarray)
.RE
.RS 1
cout << valarray<int>(vi[gslice(0,len,stride)]) << endl;
.RE
.RS 0

.RE
.RS 2
// Print a two dimensional slice out of the middle
.RE
.RS 1
valarray<size_t> len2(2);
.br
len2[0] = 3;
.br
len2[1] = 3;
.br
valarray<size_t> stride2(2);
.br
stride2[0] = 3;
.br
stride2[1] = 1;
.br
cout << valarray<int>(vi[gslice(9,len2,stride2)]) << endl;
.RE
.RS 0

.RE
.RS 2
// Print another two dimensional slice out of the middle
.br
// but orthogonal to one we just did
.RE
.RS 1
stride2[0] = 9;
.br
stride2[1] = 1;
.br
cout << valarray<int>(vi[gslice(3,len2,stride2)]) << endl;
.RE
.RS 0

.RE
.RS 2
// Print out the last plane in the middle,
.br
// (orthogonal to both of the previous ones)
.RE
.RS 1
stride2[0] = 3;
.br
stride2[1] = 9;
.br
cout << valarray<int>(vi[gslice(1,len2,stride2)]) << endl;
.RE
.RS 0

.RE
.RS 2
// Now how about a diagonal slice?
.br
// upper left front to lower right back
.RE
.RS 1
stride2[0] = 3;
.br
stride2[1] = 10;
.br
cout << valarray<int>(vi[gslice(0,len2,stride2)]) << endl;
.RE
.RS 2

.RE
.RS 1
return 0;
.RE
.RS 0
}

.br
.RE
.RS 0
Program Output



.br

.br
[0,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,9,2,3,4,5,6,7,8,9,10]
.br
[0,1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8,9,2,3,4,5,6,7,8,9,10]
.br
[1,2,3,4,5,6,7,8,9]
.br
[3,4,5,4,5,6,5,6,7]
.br
[1,2,3,4,5,6,7,8,9]
.br
[0,2,4,3,5,7,6,8,10]



.SH  WARNINGS


If your compiler does not support namespaces, then you do not need the using declaration for \f2std\fP.



.SH  SEE ALSO


valarray, slice_array, slice, gslice_array, mask_array, indirect_array