indirect_array(3C++) - indirect_array(3C++)
Standard C++ Library Copyright 1998, Rogue Wave Software, Inc.
NAMEindirect_array
- A numeric array class used to represent elements selected from a
valarray.
SYNOPSIS
#include <valarray>
template <class T>
class indirect_array ;
DESCRIPTION
indirect_array<T> creates a selective view into a valarray. Indi‐
rect_arrays are produced by applying the indirect subscript operator to
a valarray. The indirect array produced by this subscript contains only
the elements of the valarray whose indices appear as values in the
argument. The elements in an indirect_array are references to selected
elements in the valarray (so changing an element in the indirect_array
really changes the corresponding element in the valarray). An indi‐
rect_array does not itself hold any distinct elements. The template
cannot be instantiated directly since all its constructors are private.
However, you can copy an indirect_array to a valarray using either the
valarray copy constructor or the assignment operator. Reference seman‐
tics are lost at that point.
INTERFACE
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);
};
CONSTRUCTORSindirect_array();
indirect_array(const indirect_array&);
All indirect_array constructors are private and cannot be called directly.
This prevents copy construction of indirect_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 an indirect_array never holds any elements itself;
it simply refers to selected elements in the valarray used to generate it.
indirect_array<T>&
operator=(const indirect-_array<T>& x);
Private assignment operator. Cannot be called directly, thus preventing
assignment between indirect_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 an indi‐
rect_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);
Assigns x to the selected elements of the valarray that self refers to.
EXAMPLE
//
// indirect_array.cpp
//
#include "valarray.h" // Contains a valarray stream inserter
using namespace std;
int main(void)
{
int ibuf[10] = {0,1,2,3,4,5,6,7,8,9};
size_t sbuf[6] = {0,2,3,4,7,8};
// create a valarray of ints
valarray<int> vi(ibuf,10);
// create a valarray of indices for a selector
valarray<size_t> selector(sbuf,6);
// print out the valarray<int>
cout << vi << endl;
// Get a indirect_array
// and assign that indirect to another valarray
indirect_array<int> select = vi[selector];
valarray<int> vi3 = select;
// print out the selective array
cout << vi3 << endl;
// Double the selected values
select += vi3;
// print out vi1 again
cout << vi << endl;
return 0;
}
Program Output
[0,1,2,3,4,5,6,7,8,9]
[0,2,3,4,7,8]
[0,1,4,6,8,5,6,14,16,9]
WARNINGS
If your compiler does not support namespaces, then you do not need the
using declaration for std.
SEE ALSO
slice, slice_array, valarray, gslice, gslice_array, mask_array
Rogue Wave Software 02 Apr 1998 indirect_array(3C++)