gslice();
gslice(size_t start, const valarray<size_t>& lengths,
const valarray<size_t>& strides);
gslice(const gslice&);
The default constructor is equivalent to gslice(0, valarray<size_t>(), valarray<size_t>()). The constructor with arguments builds a gslice based on a specification of start, lengths, and strides, as explained in the previous section.