diff --git a/lib/common.ml b/lib/common.ml
index 2d14d78..9cefb05 100644
--- a/lib/common.ml
+++ b/lib/common.ml
@@ -59,6 +59,8 @@ module Seq = struct
     if n < 0 then invalid_arg "Seq.take";
     take_aux n xs
 
+  let ints i = fun () -> Cons (i, ints (succ i))
+
   let range a b = take (b - a + 1) (ints a)
   let (--) a b = range a b