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| author | Adrian Kummerlaender | 2015-02-08 20:38:00 +0100 |
|---|---|---|
| committer | Adrian Kummerlaender | 2015-02-08 20:38:00 +0100 |
| commit | beb46377c075ccc07a22b45771f8ad993a4e088e (patch) | |
| tree | feffecf2f07b8f672cd1fcee80a63291824b7b04 /src/list | |
| parent | dd504e4fcbf73750097024dce397754dc5883386 (diff) | |
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Implemented higher order `Sort` list operation
* _Quicksort_ is the algorithm of choice
** it lends itself quite well to the _TypeAsValue_ approach because of its recursive nature
** this required implementation of a `Drop` counterpart to `Take`
* the middle item of a given list is selected as the _pivot_ element
* the `List` list contructor had to be expanded to allow `void` arguments inside its variadic parameter pack
* added appropriate test cases
Diffstat (limited to 'src/list')
| -rw-r--r-- | src/list/list.h | 11 | ||||
| -rw-r--r-- | src/list/operation/higher/sort.h | 46 |
2 files changed, 57 insertions, 0 deletions
diff --git a/src/list/list.h b/src/list/list.h index 2e335e2..d2a5cb0 100644 --- a/src/list/list.h +++ b/src/list/list.h @@ -21,6 +21,16 @@ struct List<Head> { typedef typename Cons<Head, void>::type type; }; +template <typename Head> +struct List<Head, void> { + typedef typename List<Head>::type type; +}; + +template <typename... Tail> +struct List<void, Tail...> { + typedef typename List<Tail...>::type type; +}; + template < typename Type, Type... Values @@ -40,6 +50,7 @@ using Tail = typename Cdr<Cons>::type; #include "operation/basic.h" #include "operation/nth.h" #include "operation/take.h" +#include "operation/drop.h" #include "operation/append.h" #include "operation/concatenate.h" diff --git a/src/list/operation/higher/sort.h b/src/list/operation/higher/sort.h new file mode 100644 index 0000000..0ff5c40 --- /dev/null +++ b/src/list/operation/higher/sort.h @@ -0,0 +1,46 @@ +#ifndef TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_SORT_H_ +#define TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_SORT_H_ + +#include "filter.h" +#include "list/operation/concatenate.h" + +namespace tav { + +template < + template<typename, typename> class Comparator, + typename Sequence +> +class Sort { + private: + using index = Divide<typename Length<Sequence>::type, Size<2>>; + using pivot = typename Nth<index, Sequence>::type; + + using sequence_sans_pivot = typename Append< + typename Take<index, Sequence>::type, + typename Drop<Add<index, Size<1>>, Sequence>::type + >::type; + + template <typename X> + using comparator_wrapper = Comparator<pivot, X>; + + using lhs = typename Filter<comparator_wrapper, sequence_sans_pivot>::type; + using rhs = typename Remove<comparator_wrapper, sequence_sans_pivot>::type; + + public: + typedef typename Concatenate< + typename List< + typename Sort<Comparator, lhs>::type, + typename List<pivot>::type, + typename Sort<Comparator, rhs>::type + >::type + >::type type; +}; + +template <template<typename, typename> class Comparator> +struct Sort<Comparator, void> { + typedef void type; +}; + +} + +#endif // TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_SORT_H_ |