mirror of
https://github.com/triqs/dft_tools
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93 lines
2.7 KiB
ReStructuredText
93 lines
2.7 KiB
ReStructuredText
.. highlight:: c
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Compatibility with STL and iterators, Interaction with STL
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##################################################################
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The arrays are compatible with STL containers and algorithms.
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Iterators
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================
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Standard iterators are provided that model the boost Mutable_ForwardIterator and ForwardIterator concepts
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(and hence are STL compliant).
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The iterator implements also two additionnal methods :
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* it can be casted to a bool : it is true iif the iteration is not at end.
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* it.indices() : returns const & to the indices at the point of the iteration.
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Examples::
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array<long,2> A (2,3);
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for (auto it = A.begin(); it; ++it) *it =it.indices()[0] + 10 *it.indices()[1] ;
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//for (array<long,2>::iterator it = A.begin(); it; ++it) *it =it.indices()[0] + 10 *it.indices()[1] ;
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Indices generators
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================================
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The domain have an index generator that enumerates the indices in the domain.
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Examples::
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array<long,2> A (2,3);
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for (auto it = A.indexmap().domain().begin(); it; ++it) cout<<" "<<*it<<endl;
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The indices can also be produces in a custom order ::
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typedef IndexMaps::cuboid_index_generator< array<long,2>::indexmap_type::domain_type, Permutations::permutation<0,1> > it_type;
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for (it_type it(A.indexmap().domain()); it; ++it) cout<<" "<<*it<<endl;
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.. warning::
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improve this : too long, by passing a parameter ... of the Permutation type.... with default, not used, to begin....
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something like :
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for (auto it = A.indexmap().domain().begin(permutation<0,1>()); it; ++it) cout<<" "<<*it<<endl;
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Using STL containers and algorithms
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===================================================================
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* `Regular classes` have a standard value semantics, which enable them
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to be used in STL containers, like vector, list, map, unordered_map ...
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.. warning::
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Views can not be used in STL containers. They have no default constructors.
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* For example, one can make a vector of arrays ... ::
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array<long,2> A (2,3);
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std::vector<array<long,2> > VV;
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VV.push_back(A);
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* ... or a map ::
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std::map<string, array<long,2> > MAP;
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MAP["1"] = A;
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* We can put a std::vector in an array ... ::
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std::vector<int> V (10);
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array<int,1 > B(V.size()), C(V.size());
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std::copy(V.begin(),V.end(),B.begin());
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* ... or in reverse ::
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std::copy(B.begin(),B.end(),V.begin());
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* ... or use other algorithms of std::
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bool te(int x) { return (x<25);}
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//....
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cout<<" max(B) "<< *std::max_element(B.begin(),B.end())<<endl;
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std::replace_if (B.begin(), B.end(), te, 0);
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std::swap(B,C);
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.. warning::
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It works, but it may not be optimal. For example, swap is certainly not optimal [ to be improved].
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