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| author | Adrian Kummerlaender | 2015-02-19 13:45:07 +0100 |
|---|---|---|
| committer | Adrian Kummerlaender | 2015-02-19 13:45:07 +0100 |
| commit | a8bec66b05eece7b8a39102fb1b0ba8f778eb9fe (patch) | |
| tree | c1a6c4b1c6cba5ba1d87499a220f76eab59673c3 | |
| parent | 9bb66d9c1d8a7bf5bf02f5a7c400894e928d2a95 (diff) | |
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Reimplemented `Find` in terms of `ListIndex`
* `ListIndex` already implements the necessary partial template specializations for finding elements matching a predicate
* reimplemented `Cond` using `detail::find_variadic` as `Find` depends on `Apply` which in turn depends on `Cond`
** it is useful if core functionality such as the branched conditional `Cond` do not require higher order functionality such as `Find`
*** otherwise one can not use core functionality in the implementation of higher order functionality
* introduced `utility::predicate_guard` helper template
** checks a given value using a predicate and only forwards the value to the guarded function if this check is successful
** if check is unsuccessful it returns a surrogate value simmilar to `utility::predicate_assurance`
| -rw-r--r-- | src/conditional/cond.h | 14 | ||||
| -rw-r--r-- | src/list/detail/find_variadic.h | 40 | ||||
| -rw-r--r-- | src/list/detail/fold_variadic.h | 6 | ||||
| -rw-r--r-- | src/list/operation/higher/find.h | 38 | ||||
| -rw-r--r-- | src/utility/predicate.h | 22 |
5 files changed, 81 insertions, 39 deletions
diff --git a/src/conditional/cond.h b/src/conditional/cond.h index eeb31b6..8a34f79 100644 --- a/src/conditional/cond.h +++ b/src/conditional/cond.h @@ -1,10 +1,7 @@ #ifndef TYPEASVALUE_SRC_CONDITIONAL_COND_H_ #define TYPEASVALUE_SRC_CONDITIONAL_COND_H_ -#include <type_traits> - -#include "list/list.h" -#include "list/operation/higher/find.h" +#include "list/detail/find_variadic.h" namespace tav { @@ -16,12 +13,9 @@ using cond_predicate = IsTrue<Car<Pair>>; } template <typename... Branches> -using Cond = Cdr< - Find< - detail::cond_predicate, - List<Branches...> - > ->; +using Cond = Cdr<Eval< + detail::find_variadic<detail::cond_predicate, Branches...> +>>; } diff --git a/src/list/detail/find_variadic.h b/src/list/detail/find_variadic.h new file mode 100644 index 0000000..824f385 --- /dev/null +++ b/src/list/detail/find_variadic.h @@ -0,0 +1,40 @@ +#ifndef TYPEASVALUE_SRC_LIST_DETAIL_FIND_VARIADIC_H_ +#define TYPEASVALUE_SRC_LIST_DETAIL_FIND_VARIADIC_H_ + +#include "type.h" +#include "conditional/if.h" + +namespace tav { + +namespace detail { + +template < + template<typename> class Predicate, + typename Head, + typename... Tail +> +struct find_variadic { + typedef If< + Eval<Predicate<Head>>, + Head, + Eval<find_variadic<Predicate, Tail...>> + > type; +}; + +template < + template<typename> class Predicate, + typename Last +> +struct find_variadic<Predicate, Last> { + typedef If< + Eval<Predicate<Last>>, + Last, + void + > type; +}; + +} + +} + +#endif // TYPEASVALUE_SRC_LIST_DETAIL_FIND_VARIADIC_H_ diff --git a/src/list/detail/fold_variadic.h b/src/list/detail/fold_variadic.h index e02b604..2b4fdd8 100644 --- a/src/list/detail/fold_variadic.h +++ b/src/list/detail/fold_variadic.h @@ -21,10 +21,10 @@ struct fold_variadic { template < template <typename, typename> class Function, - typename Head + typename Last > -struct fold_variadic<Function, Head> { - typedef Function<Head, void> type; +struct fold_variadic<Function, Last> { + typedef Function<Last, void> type; }; } diff --git a/src/list/operation/higher/find.h b/src/list/operation/higher/find.h index 48533b7..aeb0c2a 100644 --- a/src/list/operation/higher/find.h +++ b/src/list/operation/higher/find.h @@ -1,39 +1,25 @@ #ifndef TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_FIND_H_ #define TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_FIND_H_ -#include "type.h" -#include "conditional/if.h" +#include "utility/predicate.h" +#include "function/apply.h" +#include "list/operation/nth.h" +#include "list_index.h" namespace tav { -namespace detail { - -template < - template<typename> class Predicate, - typename Current -> -struct Find { - typedef If< - Eval<Predicate<Head<Current>>>, - Head<Current>, - Eval<Find<Predicate, Tail<Current>>> - > type; -}; - -template < - template<typename> class Predicate -> -struct Find<Predicate, void> { - typedef Boolean<false> type; -}; - -} - template < template<typename> class Predicate, typename List > -using Find = Eval<detail::Find<Predicate, List>>; +using Find = typename utility::predicate_guard< + IsSize, + Apply<Nth, _0, List>::template function, + Boolean<false> +>::template check< + ListIndex<Predicate, List> +>; + } diff --git a/src/utility/predicate.h b/src/utility/predicate.h index f06fcee..e84b18f 100644 --- a/src/utility/predicate.h +++ b/src/utility/predicate.h @@ -21,6 +21,28 @@ struct predicate_assurance { >; }; +template < + template<typename...> class Function, + typename... Arguments +> +struct defer_eval { + typedef Function<Arguments...> type; +}; + +template < + template<typename> class Predicate, + template<typename> class Charge, + typename Surrogate +> +struct predicate_guard { + template <typename Value> + using check = Eval<If< + Eval<Predicate<Value>>, + defer_eval<Charge, Value>, + Surrogate + >>; +}; + template <template<typename> class Predicate> struct predicate_negator { template <typename Element> |