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nview presents a view which iterates over a given Sequence in a specified order. An nview is constructed from an arbitrary Sequence and a list of indicies specifying the elements to iterate over.
<<<<<<< .working#include <boost/fusion/view/nview.hpp> #include <boost/fusion/include/nview.hpp><<<<<<< .working
template <typename Sequence, typename Indicies> struct nview; template <typename Sequence, int I1, int I2 = -1, ...> typename result_of::nview<Sequence, I1, I2, ...>::type as_nview(Sequence& s);<<<<<<< .working
Parameter |
Description |
Default |
|---|---|---|
Sequence |
An arbitrary Fusion Forward Sequence |
|
Indicies |
A mpl::vector_c<int, ...> holding the indicies defining the required iteration order. |
|
I1, I2, I3... |
A list of integers specifying the required iteration order. |
INT_MAX for I2, I3... |
Notation
A nview type
An instance of Sequences
Instances of NV
Semantics of an expression is defined only where it differs from, or is not defined in Random Access Sequence.
Expression |
Semantics |
|---|---|
NV(s) |
Creates an nview given a sequence and a list of indicies. |
NV(nv1) |
Copy constructs an nview from another nview, nv1. |
nv1 = nv2 |
Assigns to an nview, nv1, from another nview, nv2. |
The nview internally stores a Fusion vector of references to the elements of the original Fusion Sequence
<<<<<<< .workingtypedef vector<int, char, double> vec; =======Example
typedefvector<int, char, double> vec; >>>>>>> .merge-right.r57125 typedef mpl::vector_c<int, 2, 1, 0, 2, 0> indicies; vec v1(1, 'c', 2.0); std::cout << nview<vec, indicies>(v1) << std::endl; // (2.0 c 1 2.0 1) std::cout << as_nview<2, 1, 1, 0>(v1) << std::endl; // (2.0 c c 1)