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-rw-r--r--src/list/operation/higher/query.h11
-rw-r--r--test.cc24
2 files changed, 35 insertions, 0 deletions
diff --git a/src/list/operation/higher/query.h b/src/list/operation/higher/query.h
index 29f65dc..c6eabc7 100644
--- a/src/list/operation/higher/query.h
+++ b/src/list/operation/higher/query.h
@@ -3,6 +3,7 @@
#include "fold.h"
#include "misc.h"
+#include "operation/math.h"
#include "operation/logic.h"
namespace tav {
@@ -35,6 +36,16 @@ using None = Not<
typename Any<Function, List>::type
>;
+template <
+ template<typename> class Function,
+ typename List
+>
+using Count = Fold<
+ Add,
+ tav::Size<0>,
+ typename Map<Function, List>::type
+>;
+
}
#endif // TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_QUERY_H_
diff --git a/test.cc b/test.cc
index 6476bb8..62c6f85 100644
--- a/test.cc
+++ b/test.cc
@@ -607,3 +607,27 @@ static_assert(
>::value,
"(list-tabulate 4 square) != (list 0 1 4 9)"
);
+
+// list count
+
+static_assert(
+ std::is_same<
+ tav::Size<2>,
+ tav::Count<
+ tav::Odd,
+ tav::List<tav::Int<1>, tav::Int<2>, tav::Int<3>>::type
+ >::type
+ >::value,
+ "(count odd? (list 1 2 3)) != 2"
+);
+
+static_assert(
+ std::is_same<
+ tav::Size<0>,
+ tav::Count<
+ tav::Even,
+ tav::List<tav::Int<1>, tav::Int<3>, tav::Int<5>>::type
+ >::type
+ >::value,
+ "(count even? (list 1 3 5)) != 0"
+);