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-rw-r--r--src/list/operation/higher/fold.h28
-rw-r--r--test.cc6
2 files changed, 34 insertions, 0 deletions
diff --git a/src/list/operation/higher/fold.h b/src/list/operation/higher/fold.h
new file mode 100644
index 0000000..6ad4bd7
--- /dev/null
+++ b/src/list/operation/higher/fold.h
@@ -0,0 +1,28 @@
+#ifndef TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_FOLD_H_
+#define TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_FOLD_H_
+
+namespace tav {
+
+template <
+ template<typename, typename> class Function,
+ typename Initial,
+ typename Current
+>
+struct Fold {
+ typedef typename Function<
+ Head<Current>,
+ typename Fold<Function, Initial, Tail<Current>>::type
+ >::type type;
+};
+
+template <
+ template<typename, typename> class Function,
+ typename Initial
+>
+struct Fold<Function, Initial, void> {
+ typedef Initial type;
+};
+
+}
+
+#endif // TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_FOLD_H_
diff --git a/test.cc b/test.cc
index f60adbd..e642b3a 100644
--- a/test.cc
+++ b/test.cc
@@ -5,6 +5,7 @@
#include "conditional/if.h"
#include "list/cons.h"
#include "list/list.h"
+#include "list/operation/higher/fold.h"
class TypeAsValueTest : public ::testing::Test { };
@@ -83,6 +84,11 @@ TEST_F(TypeAsValueTest, ListConcatenate) {
EXPECT_EQ(2, ( tav::Head<tav::Tail<tav::Concatenate<tav::List<tav::Int<1>>::type, tav::List<tav::Int<2>>::type>::type>>::value ));
}
+TEST_F(TypeAsValueTest, ListFold) {
+ // (fold + 0 (list 1 2 3))
+ EXPECT_EQ(6, ( tav::Fold<tav::Add, tav::Int<0>, tav::List<tav::Int<1>, tav::Int<2>, tav::Int<3>>::type>::type::value ));
+}
+
int main(int argc, char **argv) {
testing::InitGoogleTest(&argc, argv);