# Let rec trouble

From: Christopher Oliver (oliver@fritz.traverse.com)
Date: Sat Jul 25 1998 - 21:06:38 MET DST

Subject: Let rec trouble
To: caml-list@inria.fr
Date: Sat, 25 Jul 1998 15:06:38 -0400 (EDT)
From: "Christopher Oliver" <oliver@fritz.traverse.com>
Message-Id: <E0z09eQ-00007g-00@fritz.traverse.net>

I'm having trouble with the syntax of let rec. Consider the following
program for computing Van der Waerden's bound:

open Num
open Nat
open Big_int
open Ratio

let rec n k l =
let rec m i =
if i =/ Int 0 then
Int 1 else
Int 2
*/ (m (pred_num i))
*/ (n (k **/ (m (pred_num i))) (pred_num l)) in
if l =/ Int 2 then succ_num k else m k;;

print_string (string_of_num (n (Int 3) (Int 3)));;

I would like to restrict the lexical scope of 'n' by replacing the first
double semicolon with 'in.' I nest m precisely to capture k and l in m's
lexical environment. Why is this use forbidden? I.e. Why shouldn't I be
able to write:

let rec n k l =
let rec m i =
if i =/ Int 0 then
Int 1 else
Int 2
*/ (m (pred_num i))
*/ (n (k **/ (m (pred_num i))) (pred_num l)) in
if l =/ Int 2 then succ_num k else m k
in
print_string (string_of_num (n (Int 3) (Int 3)));;

I would prefer not to define a top level symbol, and this seems an
inconsistancy. Am I missing something?

```--
Christopher Oliver                     Traverse Internet
Systems Coordinator                    223 Grandview Pkwy, Suite 108
oliver@traverse.net                    Traverse City, Michigan, 49684
let magic f = fun x -> x and more_magic n f = fun x -> f ((n f) x);;
```

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