Implemented `Iota` list constructor

* recursively generates a list of `Count` elements starting at `Initial` and consecutively adding `Step`
** as most functionality of this library this function was modeled after its _Scheme_ equivalent `iota`
** it may be used as the foundation of a set of higher order list generators including e.g. `list-tabulate`
* added appropriate test cases

2 files changed, 73 insertions, 0 deletions

diff --git a/src/list/iota.h b/src/list/iota.h
new file mode 100644
index 0000000..9a8d22d
--- /dev/null
+++ b/src/list/iota.h
@@ -0,0 +1,34 @@
+#ifndef TYPEASVALUE_SRC_LIST_IOTA_H_
+#define TYPEASVALUE_SRC_LIST_IOTA_H_
+
+#include "operation/math.h"
+
+namespace tav {
+
+template <
+	typename Count,
+	typename Initial,
+	typename Step
+>
+struct Iota {
+	typedef Cons<
+		Initial,
+		typename Iota<
+			Substract<Count, Size<1>>,
+			Add<Initial, Step>,
+			Step
+		>::type
+	> type;
+};
+
+template <
+	typename Initial,
+	typename Step
+>
+struct Iota<Size<1>, Initial, Step> {
+	typedef Cons<Initial, void> type;
+};
+
+}
+
+#endif  // TYPEASVALUE_SRC_LIST_IOTA_H_
diff --git a/test.cc b/test.cc
index b945899..173aa19 100644
--- a/test.cc
+++ b/test.cc
@@ -5,6 +5,7 @@
 
 #include "list/cons.h"
 #include "list/list.h"
+#include "list/iota.h"
 #include "list/operation/reverse.h"
 #include "list/operation/contains.h"
 #include "list/operation/higher/fold.h"
@@ -507,3 +508,41 @@ static_assert(
 	>::value,
 	"(length (concatenate (list (list 1 2) (list 3) (list 4 5 6)))) != 6"
 );
+
+// list iota
+
+static_assert(
+	std::is_same<
+		tav::List<tav::Int<1>, tav::Int<2>, tav::Int<3>>::type,
+		tav::Iota<
+			tav::Size<3>,
+			tav::Int<1>,
+			tav::Int<1>
+		>::type
+	>::value,
+	"(iota 3 1 1) != (list 1 2 3)"
+);
+
+static_assert(
+	std::is_same<
+		tav::List<tav::Int<0>, tav::Int<2>, tav::Int<4>, tav::Int<6>, tav::Int<8>>::type,
+		tav::Iota<
+			tav::Size<5>,
+			tav::Int<0>,
+			tav::Int<2>
+		>::type
+	>::value,
+	"(iota 5 0 2) != (list 0 2 4 6 8)"
+);
+
+static_assert(
+	std::is_same<
+		tav::List<tav::Int<5>, tav::Int<4>, tav::Int<3>, tav::Int<2>, tav::Int<1>>::type,
+		tav::Iota<
+			tav::Size<5>,
+			tav::Int<5>,
+			tav::Int<-1>
+		>::type
+	>::value,
+	"(iota 5 5 -1) != (list 5 4 3 2 1)"
+);