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[Caml-list] [q] on implementing of "memoization"
- SooHyoung Oh
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| Date: | -- (:) |
| From: | SooHyoung Oh <shoh@d...> |
| Subject: | [Caml-list] [q] on implementing of "memoization" |
In testing "memoization" of fib function, it is OK on
let rec fib = ... and memo_fib n = memoize fib n;;
but it makes the ERROR on
let rec fib = ... and memo_fib = memoize fib;;
The error message is
This kind of expression is not allowed as right-hand side of `let rec'
Why does this error occur?
I can't find good description on ocaml manual.
One more thing:
Do you have any idea about ** generic ** and good implementation of
memoization?
The source is
----------------------------------
let lookup key table = List.assoc key !table;;
let insert key value table = table := (key, value) :: !table;;
let table = ref [];;
let memoize f n =
try
lookup n table
with
| Not_found ->
let result = f n in
insert n result table;
result
;;
let rec fib = function
| 0 -> 0
| 1 -> 1
| n -> memo_fib (n-1) + memo_fib (n-2)
and memo_fib n = memoize fib n
;;
----------------------
Thanks a lot!
---
SooHyoung Oh
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