class template
<valarray>
std::gslice_array
template <class T> gslice_array;
Valarray gslice selection
This class is used as an intermediate type returned by valarray 's subscript operator (operator[]) when used with generalized gslices .
It references the elements in the valarray object that are selected by the gslice , and overloads the assignment and compound assignment operators, allowing direct access to the elements in the selection.
The type is convertible to a valarray (see valarray constructor ), producing a new object with copies of the referred elements.
Objects of this type are obtained as the return value of a call to
valarray::operator[] . They cannot be directly
constructed nor copied. It is declared as:
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template <class T> class gslice_array {
public:
typedef T value_type;
void operator= (const valarray<T>&) const;
void operator*= (const valarray<T>&) const;
void operator/= (const valarray<T>&) const;
void operator%= (const valarray<T>&) const;
void operator+= (const valarray<T>&) const;
void operator-= (const valarray<T>&) const;
void operator^= (const valarray<T>&) const;
void operator&= (const valarray<T>&) const;
void operator|= (const valarray<T>&) const;
void operator<<= (const valarray<T>&) const;
void operator>>= (const valarray<T>&) const;
void operator=(const T&);
~gslice_array();
private:
gslice_array();
gslice_array(const gslice_array&);
gslice_array& operator= (const gslice_array&);
};
Objects of this type are obtained as the return value of a call to
valarray::operator[] . They cannot be
default-constructed, but can be copied. It is declared as:
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template <class T> class gslice_array {
public:
typedef T value_type;
void operator= (const valarray<T>&) const;
void operator*= (const valarray<T>&) const;
void operator/= (const valarray<T>&) const;
void operator%= (const valarray<T>&) const;
void operator+= (const valarray<T>&) const;
void operator-= (const valarray<T>&) const;
void operator^= (const valarray<T>&) const;
void operator&= (const valarray<T>&) const;
void operator|= (const valarray<T>&) const;
void operator<<= (const valarray<T>&) const;
void operator>>= (const valarray<T>&) const;
void operator=(const T&) const;
gslice_array() = delete;
gslice_array(const gslice_array&);
const gslice_array& operator= (const gslice_array&) const;
~gslice_array();
};
Example
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// gslice_array example
#include <iostream> // std::cout
#include <cstddef> // std::size_t
#include <valarray> // std::valarray, std::gslice
int main ()
{
std::valarray<int> foo (14);
for (int i=0; i<14; ++i) foo[i]=i;
std::size_t start=1;
std::size_t lengths[]= {2,3};
std::size_t strides[]= {7,2};
std::gslice mygslice (start,
std::valarray<std::size_t>(lengths,2),
std::valarray<std::size_t>(strides,2));
foo[mygslice] = 0;
std::cout << "foo:\n";
for (std::size_t n=0; n<foo.size(); n++)
std::cout << ' ' << foo[n];
std::cout << '\n';
return 0;
}
Output:
0 0 2 0 4 0 6 7 0 9 0 11 0 13