
Valarray helpers
A numeric array class used to represent elements selected from a valarray.
| Member Functions | |
| operator%=() operator&=() operator>>=() operator<<=() operator*=() operator+=() |
operator-=() operator/=() operator=() operator^=() |
#include <valarray> template <class T> class indirect_array ;
indirect_array<T> creates a selective view into a valarray. Indirect_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 indirect_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 semantics are lost at that point.
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);
};
indirect_array(); indirect_array(const indirect_array&);
All indirect_array constructors are private and cannot be called directly. This prevents copy construction of indirect_arrays.
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.
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 indirect_array never holds any elements itself; it simply refers to selected elements in the valarray used to generate it.
void operator=(const T& x);
Assigns x to the selected elements of the valarray that self refers to.
//
// 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]
If your compiler does not support namespaces, then you do not need the using declaration for std.
valarray, slice_array, slice, gslice, gslice_array, mask_array