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authorAdrian Kummerlaender2015-02-17 22:47:56 +0100
committerAdrian Kummerlaender2015-02-17 22:47:56 +0100
commitaf5662781840ac45c21cbf14cbc7973bcf39d1da (patch)
tree9264a8e75ea7d87319f4298d47e97c47c58813fb
parentc31731d0131c08c4ced091449764561eb3e5e2ab (diff)
Reimplemented `TakeWhile` and `DropWhile` in terms of `ListIndex`
* new higher order list operation `ListIndex` returns the index of the first list element satisfying a given predicate function ** this enables finding the split index required for both `TakeWhile` and `DropWhile` ** actual list manipulation is then performed using lower order `Take` or `Drop` ** analogously to `list-index` in SRFI-1 ** added appropriate test case * added higher order predicate utility function `utility::predicate_assurance` ** as its name implies this function enables assuring that a value satisfies a given predicate *** if this is not the case a surrogate value is returned instead ** this is used to return a appropriate size value if the `ListIndex` call fails because no element satisfies its predicate ** `detail::predicate_negator` was moved from `Remove`'s implementation details into the newly introduced `utility` namespace *** as it is required by both `TakeWhile` and `DropWhile` in addition to `Remove` * continuation of 8e49cc6
-rw-r--r--src/list/operation/higher/drop_while.h42
-rw-r--r--src/list/operation/higher/list_index.h45
-rw-r--r--src/list/operation/higher/remove.h13
-rw-r--r--src/list/operation/higher/take_while.h45
-rw-r--r--src/utility/predicate.h34
-rw-r--r--test.cc25
6 files changed, 138 insertions, 66 deletions
diff --git a/src/list/operation/higher/drop_while.h b/src/list/operation/higher/drop_while.h
index 021698f..1207020 100644
--- a/src/list/operation/higher/drop_while.h
+++ b/src/list/operation/higher/drop_while.h
@@ -1,38 +1,28 @@
#ifndef TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_DROP_WHILE_H_
#define TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_DROP_WHILE_H_
-#include "conditional/if.h"
+#include "list_index.h"
+#include "list/operation/drop.h"
+#include "utility/predicate.h"
namespace tav {
-namespace detail {
-
-template <
- template<typename> class Predicate,
- typename Current
->
-struct DropWhile {
- typedef If<
- Eval<Predicate<Head<Current>>>,
- Eval<DropWhile<Predicate, Tail<Current>>>,
- Current
- > type;
-};
-
-template <
- template<typename> class Predicate
->
-struct DropWhile<Predicate, void> {
- typedef void type;
-};
-
-}
-
template <
template<typename> class Predicate,
- typename Current
+ typename List
>
-using DropWhile = Eval<detail::DropWhile<Predicate, Current>>;
+using DropWhile = Drop<
+ typename utility::predicate_assurance<
+ utility::predicate_negator<std::is_void>::template function,
+ Length<List>
+ >::template assure<
+ ListIndex<
+ utility::predicate_negator<Predicate>::template function,
+ List
+ >
+ >,
+ List
+>;
}
diff --git a/src/list/operation/higher/list_index.h b/src/list/operation/higher/list_index.h
new file mode 100644
index 0000000..bbf43ee
--- /dev/null
+++ b/src/list/operation/higher/list_index.h
@@ -0,0 +1,45 @@
+#ifndef TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_LIST_INDEX_H_
+#define TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_LIST_INDEX_H_
+
+#include "operation/math.h"
+
+namespace tav {
+
+namespace detail {
+
+template <
+ template<typename> class Predicate,
+ typename List,
+ typename Index = Size<0>
+>
+struct index_of_first {
+ typedef If<
+ Eval<Predicate<Head<List>>>,
+ Index,
+ Eval<index_of_first<
+ Predicate,
+ Tail<List>,
+ Add<Index, Size<1>>
+ >>
+ > type;
+};
+
+template <
+ template<typename> class Predicate,
+ typename Index
+>
+struct index_of_first<Predicate, void, Index> {
+ typedef void type;
+};
+
+}
+
+template <
+ template<typename> class Predicate,
+ typename List
+>
+using ListIndex = Eval<detail::index_of_first<Predicate, List>>;
+
+}
+
+#endif // TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_LIST_INDEX_H_
diff --git a/src/list/operation/higher/remove.h b/src/list/operation/higher/remove.h
index 598f5a6..6770359 100644
--- a/src/list/operation/higher/remove.h
+++ b/src/list/operation/higher/remove.h
@@ -2,25 +2,16 @@
#define TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_REMOVE_H_
#include "filter.h"
+#include "utility/predicate.h"
namespace tav {
-namespace detail {
-
-template <template<typename> class Predicate>
-struct predicate_negator {
- template <typename Element>
- using function = Not<Predicate<Element>>;
-};
-
-}
-
template <
template<typename> class Predicate,
typename List
>
using Remove = Filter<
- detail::predicate_negator<Predicate>::template function,
+ utility::predicate_negator<Predicate>::template function,
List
>;
diff --git a/src/list/operation/higher/take_while.h b/src/list/operation/higher/take_while.h
index dec5551..f9fc3aa 100644
--- a/src/list/operation/higher/take_while.h
+++ b/src/list/operation/higher/take_while.h
@@ -1,41 +1,28 @@
#ifndef TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_TAKE_WHILE_H_
#define TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_TAKE_WHILE_H_
-#include "conditional/if.h"
+#include "list_index.h"
+#include "list/operation/take.h"
+#include "utility/predicate.h"
namespace tav {
-namespace detail {
-
-template <
- template<typename> class Predicate,
- typename Current
->
-struct TakeWhile {
- typedef If<
- Eval<Predicate<Head<Current>>>,
- Cons<
- Head<Current>,
- Eval<TakeWhile<Predicate, Tail<Current>>>
- >,
- void
- > type;
-};
-
-template <
- template<typename> class Predicate
->
-struct TakeWhile<Predicate, void> {
- typedef void type;
-};
-
-}
-
template <
template<typename> class Predicate,
- typename Current
+ typename List
>
-using TakeWhile = Eval<detail::TakeWhile<Predicate, Current>>;
+using TakeWhile = Take<
+ typename utility::predicate_assurance<
+ utility::predicate_negator<std::is_void>::template function,
+ Length<List>
+ >::template assure<
+ ListIndex<
+ utility::predicate_negator<Predicate>::template function,
+ List
+ >
+ >,
+ List
+>;
}
diff --git a/src/utility/predicate.h b/src/utility/predicate.h
new file mode 100644
index 0000000..f06fcee
--- /dev/null
+++ b/src/utility/predicate.h
@@ -0,0 +1,34 @@
+#ifndef TYPEASVALUE_SRC_UTILITY_PREDICATE_H_
+#define TYPEASVALUE_SRC_UTILITY_PREDICATE_H_
+
+#include "conditional/if.h"
+#include "operation/logic.h"
+
+namespace tav {
+
+namespace utility {
+
+template <
+ template<typename> class Predicate,
+ typename Surrogate
+>
+struct predicate_assurance {
+ template <typename Value>
+ using assure = If<
+ Eval<Predicate<Value>>,
+ Value,
+ Surrogate
+ >;
+};
+
+template <template<typename> class Predicate>
+struct predicate_negator {
+ template <typename Element>
+ using function = Not<Predicate<Element>>;
+};
+
+}
+
+}
+
+#endif // TYPEASVALUE_SRC_UTILITY_PREDICATE_H_
diff --git a/test.cc b/test.cc
index 2f95561..6a957b1 100644
--- a/test.cc
+++ b/test.cc
@@ -12,6 +12,7 @@
#include "list/operation/higher/remove.h"
#include "list/operation/higher/partition.h"
#include "list/operation/higher/query.h"
+#include "list/operation/higher/list_index.h"
#include "list/operation/higher/find.h"
#include "list/operation/higher/take_while.h"
#include "list/operation/higher/drop_while.h"
@@ -906,6 +907,30 @@ static_assert(
"(count even? (list 1 3 5)) != 0"
);
+// list index
+
+static_assert(
+ std::is_same<
+ tav::Size<2>,
+ tav::ListIndex<
+ tav::Even,
+ tav::List<tav::Int<1>, tav::Int<3>, tav::Int<4>, tav::Int<6>>
+ >
+ >::value,
+ "(list-index even? (list 1 3 4 6)) != 2"
+);
+
+static_assert(
+ std::is_same<
+ void,
+ tav::ListIndex<
+ tav::Even,
+ tav::List<tav::Int<1>, tav::Int<3>, tav::Int<5>>
+ >
+ >::value,
+ "(list-index even? (list 1 3 5)) != void"
+);
+
// list find
static_assert(