5.5 KiB
[valarray.sub]
29 Numerics library [numerics]
29.6 Numeric arrays [numarray]
29.6.2 Class template valarray [template.valarray]
29.6.2.5 Subset operations [valarray.sub]
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) shall exist.
valarray operator[](slice slicearr) const;
Returns: A valarray containing those elements of the controlled sequence designated by slicearr.
[Example 1: const valarray v0("abcdefghijklmnop", 16);// v0[slice(2, 5, 3)] returns valarray("cfilo", 5) â end example]
slice_array<T> operator[](slice slicearr);
Returns: An object that holds references to elements of the controlled sequence selected by slicearr.
[Example 2: valarray v0("abcdefghijklmnop", 16); valarray v1("ABCDE", 5); v0[slice(2, 5, 3)] = v1;// v0 == valarray("abAdeBghCjkDmnEp", 16); â end example]
valarray operator[](const gslice& gslicearr) const;
Returns: A valarray containing those elements of the controlled sequence designated by gslicearr.
[Example 3: const valarray 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("dfhkmo", 6) â 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 4: valarray v0("abcdefghijklmnop", 16); valarray 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("abcAeBgCijDlEnFp", 16) â end example]
valarray operator[](const valarray<bool>& boolarr) const;
Returns: A valarray containing those elements of the controlled sequence designated by boolarr.
[Example 5: const valarray v0("abcdefghijklmnop", 16);const bool vb[] = { false, false, true, true, false, true };// v0[valarray(vb, 6)] returns// valarray("cdf", 3) â 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 6: valarray v0("abcdefghijklmnop", 16); valarray v1("ABC", 3);const bool vb[] = { false, false, true, true, false, true }; v0[valarray(vb, 6)] = v1;// v0 == valarray("abABeCghijklmnop", 16) â end example]
valarray operator[](const valarray<size_t>& indarr) const;
Returns: A valarray containing those elements of the controlled sequence designated by indarr.
[Example 7: const valarray v0("abcdefghijklmnop", 16);const size_t vi[] = { 7, 5, 2, 3, 8 };// v0[valarray<size_t>(vi, 5)] returns// valarray("hfcdi", 5) â 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 8: valarray v0("abcdefghijklmnop", 16); valarray v1("ABCDE", 5);const size_t vi[] = { 7, 5, 2, 3, 8 }; v0[valarray<size_t>(vi, 5)] = v1;// v0 == valarray("abCDeBgAEjklmnop", 16) â end example]