[ocaml/en] Change the example of mutually recursive functions

Change the example to a meaningful and self-contained example of
mutually recursive functions.

1 files changed, 10 insertions, 5 deletions

diff --git a/ocaml.html.markdown b/ocaml.html.markdown
index f9db7080..b30d920b 100644
--- a/ocaml.html.markdown
+++ b/ocaml.html.markdown
@@ -144,11 +144,16 @@ x + y ;;
 (* Alternatively you can use "let ... and ... in" construct.
    This is especially useful for mutually recursive functions,
    with ordinary "let .. in" the compiler will complain about
-   unbound values.
-   It's hard to come up with a meaningful but self-contained
-   example of mutually recursive functions, but that syntax
-   works for non-recursive definitions too. *)
-let a = 3 and b = 4 in a * b ;;
+   unbound values. *)
+let rec
+  is_even = function
+  | 0 -> true
+  | n -> is_odd (n-1)
+and
+  is_odd = function
+  | 0 -> false
+  | n -> is_even (n-1)
+;;
 
 (* Anonymous functions use the following syntax: *)
 let my_lambda = fun x -> x * x ;;