gslice_array Class

 

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An internal, auxiliary template class that supports general slice objects by providing operations between subset arrays defined by the general slice of a valarray.

template <class Type>  
class gslice_array : public gsplice {  
public:  
    typedef Type value_type;  
    void operator=(const valarray<Type>& x) const;

 
 
    void operator=(const Type& x) const;

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

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

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

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

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

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

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

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

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

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

 
 
// The rest is private or implementation defined  
}  

The class describes an object that stores a reference to an object va of class valarray<Type>, along with an object gs of class gslice which describes the sequence of elements to select from the valarray<Type> object.

You construct a gslice_array<Type> object only by writing an expression of the form va[gs]. The member functions of class gslice_array then behave like the corresponding function signatures defined for valarray<Type>, except that only the sequence of selected elements is affected.

The template class is created indirectly by certain valarray operations and cannot be used directly in the program. An internal auxiliary template class instead is used by the slice subscript operator:

gslice_array< Type> valarray< Type>:: operator[] ( constgslice&).

You construct a gslice_array<Type> object only by writing an expression of the form va[gsl], for a slice gsl of valarray va. The member functions of class gslice_array then behave like the corresponding function signatures defined for valarray<Type>, except that only the sequence of selected elements is affected. The sequence controlled by the gslice_array is defined by the three parameters of the slice constructor, the index of the first element in the first slice, the number of elements in each slice, and the distance between the elements in each slice.

In the following example:

const size_t lv[] = {2, 3};  
const size_t dv[] = {7, 2};  
const valarray<size_t> len(lv, 2), str(dv, 2);

// va[gslice(3, len, str)] selects elements with  
//   indices 3, 5, 7, 10, 12, 14  

The indices must be valid for the procedure to be valid.

See the example for gslice::gslice for an example of how to declare and use a slice_array.

Header: <valarray>

Namespace: std

Thread Safety in the C++ Standard Library

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