* arith.c (wrap_star, wrap): New functions.

* eval.c (eval_init): Registered wrap and wrap* intrinsics.

* lib.h (wrap_star, wrap): Declared.

* txr.1: wrap and wrap* documented.

1 files changed, 13 insertions, 0 deletions

diff --git a/arith.c b/arith.c
index 23cf66a8..00621a5d 100644
--- a/arith.c
+++ b/arith.c
@@ -938,6 +938,19 @@ divzero:
   uw_throw(numeric_error_s, lit("mod: division by zero"));
 }
 
+val wrap_star(val start, val end, val num)
+{
+  val modulus = minus(end, start);
+  val num_off = minus(num, start);
+  val num_mod = mod(num_off, modulus);
+  return plus(start, num_mod);
+}
+
+val wrap(val start, val end, val num)
+{
+  return wrap_star(start, succ(end), num);
+}
+
 static val to_float(val func, val num)
 {
   switch (type(num)) {