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53 lines
2.1 KiB
ReStructuredText
53 lines
2.1 KiB
ReStructuredText
.. _DesignSlicing:
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Slicing
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=============================================================
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In this section, IM denotes some IndexMaps.
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* We refer here to any partial view of the arrays as "slicing", i.e. subarrays, true slices, etc...
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A slicing is any (meta)-function that take an indexmap and return another one.
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* It is a meta-function that computes the type of the resulting indexmap
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* It is a function that computes the resulting indexmap.
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* The array/matrix/vector classes and their views, when called with the () operator, will :
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* forward all the arguments and their types to IndexMaps::slice, to compute the new indexmap IM2.
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* If IM2 is of dimension 0, return a value_type & or const & (it is a simple number, not an array).
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* Otherwise : return a new view, made of IM2 and the same data as for the original object.
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* Possible slices are defined by the IndexMap type.
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Slicing an class C with IndexMap I1 produces a class C2_view, with IndexMap I2,
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i.e. a new sliced IndexMap on the same data.
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* **Examples** :
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* array and array_view can be sliced :
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``
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array<T,2> A(10,10); : defines an array
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A(1,2) : element access.
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A ( 1, range(0,2) ) : 1d slice
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A( range(0,10,2), range(0,10,2)) : a 2d slice viewing every each elements with even coordinates.
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``
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* matrix, matrix_view when sliced, return vector_view or matrix_view.
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* One can be much more general : e.g. slicing the diagonal of a matrix, etc...
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* Implementation is entirely done in the IndexMaps classes, by specializing 2 templates
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(basically by writing the function IM1-> IM2).
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The rest is done by indexmap_storage_pair class, which will compute the correct view class
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depending on the view class and IM2 (view_from_tag_I_S template).
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::
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//In namespace IndexMaps::result_of
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template<typename IM, typename ArgsTuple>
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struct slice< IM, ArgsTuple> { typedef IM2 type; };
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//In namespace IndexMaps :
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template<typename IM, typename ArgsTuple>
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typename result_of::slice<IM,ArgsTuple>::type slice(IM const &, ArgsTuple args);
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