gslice_array(3C++)

Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.

NAME

gslice_array

- A numeric array class used to represent a BLAS-like slice from a valarray.

SYNOPSIS

#include <valarray>
template <class T>
class gslice_array ;

DESCRIPTION

gslice_array<T> creates a gslice view into a valarray. gslice_arrays are only produced by applying the gslice subscript operator to a valarray. The elements in a gslice_array are references to selected elements in the valarray (so changing an element in the gslice_array really changes the corresponding element in the valarray). A gslice_array does not itself hold any distinct elements. The template cannot be instantiated directly since all its constructors are private. However, you can copy a gslice_array to a valarray using either the valarray copy constructor or the assignment operator. Reference semantics are lost at that point.

INTERFACE

template <class T> class gslice_array {
public:

// types

typedef T value_type;

// destructor
~gslice_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

gslice_array();
gslice_array(const gslice_array<T>&);

// operator =

gslice_array<T>& operator= (const gslice_array<T>& array);

};

CONSTRUCTORS

gslice_array();
gslice_array(const gslice_array&);

All gslice_array constructors are private and cannot be called directly. This prevents copy construction of gslice_arrays.

ASSIGNMENT OPERATORS

void operator=(const valarray<T>& x) const;

Assigns values from x to the selected elements of the valarray that self refers to. Remember that a gslice_array never holds any elements itself; it simply refers to selected elements in the valarray used to generate it.

gslice_array<T>&
operator=(const gslice-_array<T>& x);

Private assignment operator. Cannot be called directly, thus preventing assignment between gslice_arrays.

COMPUTED ASSIGNMENT OPERATORS

void operator∗=(const valarray<T>& val) const;
void operator/=(const valarray<T>& val) const;
void operator%=(const valarray<T>& val) const;
void operator+=(const valarray<T>& val) const;
void operator-=(const valarray<T>& val) const;
void operator^=(const valarray<T>& val) const;
void operator&=(const valarray<T>& val) const;
void operator|=(const valarray<T>& val) const;
void operator<<=(const valarray<T>& val) const;
void operator>>=(const valarray<T>& val) const;

Applies the indicated operation using elements from val to the selected elements of the valarray that self refers to. Remember that a gslice_array never holds any elements itself; it simply refers to selected elements in the valarray used to generate it.

MEMBER FUNCTIONS

void operator=(const T& x) const;

Assigns x to the selected elements of the valarray that self refers to.

EXAMPLE

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

int main(void)
{

int ibuf[27] =

{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};

int buf13[9] = {13,13,13,13,13,13,13,13,13};
size_t len_buf[3] = {3,3,3};
size_t stride_buf[3] = {9,3,1};

// create a valarray of ints

valarray<int> vi(ibuf,27);

// print out the valarray

cout << vi << endl;

// Get a two dimensional diagonal slice out of the middle

valarray<size_t> len2(2);
len2[0] = 3;
len2[1] = 3;
valarray<size_t> stride2(2);
stride2[0] = 3;
stride2[1] = 10;
gslice_array<int> gsl = vi[gslice(0,len2,stride2)];

// print out the slice

cout << gsl << endl;

// Assign 13’s to everything in the slice

gsl = valarray<int>(buf13,9);

// print out the slice and our original valarray

cout << gsl << endl << vi << endl;

return 0;

}

Program Output

[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]
[0,2,4,3,5,7,6,8,10]
[13,13,13,13,13,13,13,13,13]
[13,1,2,13,4,5,13,7,8,1,13,3,4,13,6,7,13,9,2,3,13,5,6,13,8,9,13]

WARNINGS

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

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