(C++17) | ||||
| Sequence | ||||
(C++11) | ||||
(C++26) | ||||
(C++26) | ||||
(C++11) | ||||
| Associative | ||||
| Unordered associative | ||||
(C++11) | ||||
(C++11) | ||||
(C++11) | ||||
(C++11) | ||||
| Adaptors | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
(C++23) | ||||
| Views | ||||
(C++20) | ||||
(C++23) | ||||
| Tables | ||||
| Iterator invalidation | ||||
| Member function table | ||||
| Non-member function table |
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Defined in header <mdspan> | ||
template<class OffsetType,class ExtentType,class StrideType> struct strided_slice; | (since C++26) | |
An instance of every specialization ofstrided_slice is a slice specifier used instd::submdspan to select a subset of elements using a set of regularly spaced indices at a specified dimension instd::mdspan.
Eachstrided_slice objects is characterized by three data members: the offset indexs.offset, the extents.extent, and the strides.stride.
Given thats.stride is greater than zero, the number of selected indices denoted byN is determined by1+(s.extent-1)/ s.stride ifs.extent is nonzero, otherwise0. The half-open interval from which indices will be selected is given by[s.offset, s.offset+ s.extent). The sequence of selected indices is produced as follows:s.offset, ..., s.offset+(N-1)* s.stride.
This class template has no base classes or declared members other than those shown below.
Contents |
| OffsetType | - | the type of offset |
| ExtentType | - | the type of extent |
| StrideType | - | the type of stride |
| Type requirements | ||
| -All template parameters must be unsigned or signed integer types or must satisfyintegral-constant-like | ||
The program is ill-formed if the type requirement is not satisfied.
| Member type | Definition |
offset_type | OffsetType |
extent_type | ExtentType |
stride_type | StrideType |
| Member name | Definition |
offset | a starting index of typeoffset_type(public member object) |
extent | a value of typeextent_type added to offset used to define the upper bound of indices(public member object) |
stride | an increment value of typestride_type which is equivalent to the distance between two indices(public member object) |
All these members are declared with[[no_unique_address]] attribute and have default member initializers where each data member is value initialized.
Every specialization ofstrided_slice is an aggregate class which allowsaggregate initialization (including designated initialization) of data members (for instance,std::strided_slice{.offset=2, .extent=10, .stride=3}).
The slice specification ofstrided_slice takes advantage of the data memberextent, as opposed to other slice specifications that useend to indicate the upper bound value. This is because it can directly generate a static extent for subview ofstd::mdspan if bothextent andstride are of types that satisfyintegral-constant-like. This enables efficient extraction of subviews with static extents by mixing compile time values with a runtime value ofoffset.
#include <mdspan>#include <print> template<typename View,typename O=int,typename E=int,typename S=int> requires(View::extents_type::rank()==1)void print_sliced_view(View v, std::strided_slice<O, E, S> s){using index_type= View::index_type;auto subview=std::submdspan(v, s);constauto& submap= subview.mapping(); std::print("[");bool uses_comma=false;for(index_type i=0; i!= subview.extent(0);++i){if(uses_comma)std::print(", ");std::print("{}", subview[i]); uses_comma=true;} uses_comma=false;std::print("] extracted from indices [");for(index_type i=0; i!= subview.extent(0);++i){if(uses_comma)std::print(", ");std::print("{}", submap(i)+ s.offset); uses_comma=true;}std::println("]");} int main(){staticconstexprchar letters[]{'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};constexprstd::mdspan md(letters,26); print_sliced_view(md,{.offset=0, .extent=10, .stride=1}); print_sliced_view(md,{.offset=2, .extent=10, .stride=1}); print_sliced_view(md,{.offset=0, .extent=5, .stride=1}); print_sliced_view(md,{.offset=2, .extent=5, .stride=1}); print_sliced_view(md,{.offset=0, .extent=10, .stride=2}); print_sliced_view(md,{.offset=2, .extent=10, .stride=3}); print_sliced_view(md,{.offset=0, .extent=15, .stride=5}); print_sliced_view(md,{.offset=6, .extent=15, .stride=5});}
Output:
[A, B, C, D, E, F, G, H, I, J] extracted from indices [0, 1, 2, 3, 4, 5, 6, 7, 8, 9][C, D, E, F, G, H, I, J, K, L] extracted from indices [2, 3, 4, 5, 6, 7, 8, 9, 10, 11][A, B, C, D, E] extracted from indices [0, 1, 2, 3, 4][C, D, E, F, G] extracted from indices [2, 3, 4, 5, 6][A, C, E, G, I] extracted from indices [0, 2, 4, 6, 8][C, F, I, L] extracted from indices [2, 5, 8, 11][A, F, K] extracted from indices [0, 5, 10][G, L, Q] extracted from indices [6, 11, 16]
| BLAS-like slice of a valarray: starting index, length, stride (class)[edit] | |
(C++26) | returns a view of a subset of an existingmdspan(function template)[edit] |
