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authorAdrian Kummerlaender2015-02-17 22:47:56 +0100
committerAdrian Kummerlaender2015-02-17 22:47:56 +0100
commitaf5662781840ac45c21cbf14cbc7973bcf39d1da (patch)
tree9264a8e75ea7d87319f4298d47e97c47c58813fb /src/utility
parentc31731d0131c08c4ced091449764561eb3e5e2ab (diff)
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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
Diffstat (limited to 'src/utility')
-rw-r--r--src/utility/predicate.h34
1 files changed, 34 insertions, 0 deletions
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_