The member operator[] is overloaded to provide several ways to select sequences of elements from among those controlled by *this. Each of these operations returns a subset of the array. The const-qualified versions return this subset as a new valarray object. The non-const versions return a class template object which has reference semantics to the original array, working in conjunction with various overloads of operator= and other assigning operators to allow selective replacement (slicing) of the controlled sequence. In each case the selected element(s) must exist.
valarray operator[](slice slicearr) const;
Returns: A valarray containing those elements of the controlled sequence designated by slicearr. [ Example:
const valarray<char> v0("abcdefghijklmnop", 16);
// v0[slice(2, 5, 3)] returns valarray<char>("cfilo", 5)
— end example ]
slice_array<T> operator[](slice slicearr);
Returns: An object that holds references to elements of the controlled sequence selected by slicearr. [ Example:
valarray<char> v0("abcdefghijklmnop", 16);
valarray<char> v1("ABCDE", 5);
v0[slice(2, 5, 3)] = v1;
// v0 == valarray<char>("abAdeBghCjkDmnEp", 16);
— end example ]
valarray operator[](const gslice& gslicearr) const;
Returns: A valarray containing those elements of the controlled sequence designated by gslicearr. [ Example:
const valarray<char> v0("abcdefghijklmnop", 16);
const size_t lv[] = { 2, 3 };
const size_t dv[] = { 7, 2 };
const valarray<size_t> len(lv, 2), str(dv, 2);
// v0[gslice(3, len, str)] returns
// valarray<char>("dfhkmo", 6)
— end example ]
gslice_array<T> operator[](const gslice& gslicearr);
Returns: An object that holds references to elements of the controlled sequence selected by gslicearr. [ Example:
valarray<char> v0("abcdefghijklmnop", 16);
valarray<char> v1("ABCDEF", 6);
const size_t lv[] = { 2, 3 };
const size_t dv[] = { 7, 2 };
const valarray<size_t> len(lv, 2), str(dv, 2);
v0[gslice(3, len, str)] = v1;
// v0 == valarray<char>("abcAeBgCijDlEnFp", 16)
— end example ]
valarray operator[](const valarray<bool>& boolarr) const;
Returns: A valarray containing those elements of the controlled sequence designated by boolarr. [ Example:
const valarray<char> v0("abcdefghijklmnop", 16);
const bool vb[] = { false, false, true, true, false, true };
// v0[valarray<bool>(vb, 6)] returns
// valarray<char>("cdf", 3)
— end example ]
mask_array<T> operator[](const valarray<bool>& boolarr);
Returns: An object that holds references to elements of the controlled sequence selected by boolarr. [ Example:
valarray<char> v0("abcdefghijklmnop", 16);
valarray<char> v1("ABC", 3);
const bool vb[] = { false, false, true, true, false, true };
v0[valarray<bool>(vb, 6)] = v1;
// v0 == valarray<char>("abABeCghijklmnop", 16)
— end example ]
valarray operator[](const valarray<size_t>& indarr) const;
Returns: A valarray containing those elements of the controlled sequence designated by indarr. [ Example:
const valarray<char> v0("abcdefghijklmnop", 16);
const size_t vi[] = { 7, 5, 2, 3, 8 };
// v0[valarray<size_t>(vi, 5)] returns
// valarray<char>("hfcdi", 5)
— end example ]
indirect_array<T> operator[](const valarray<size_t>& indarr);
Returns: An object that holds references to elements of the controlled sequence selected by indarr. [ Example:
valarray<char> v0("abcdefghijklmnop", 16);
valarray<char> v1("ABCDE", 5);
const size_t vi[] = { 7, 5, 2, 3, 8 };
v0[valarray<size_t>(vi, 5)] = v1;
// v0 == valarray<char>("abCDeBgAEjklmnop", 16)
— end example ]