From af5662781840ac45c21cbf14cbc7973bcf39d1da Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Tue, 17 Feb 2015 22:47:56 +0100
Subject: 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

---
 test.cc | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

(limited to 'test.cc')

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(
-- 
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