Message-Id: <199706021620.JAA20114@blaze.accessone.com>
From: "Dwight VandenBerghe" <dwight@pentasoft.com>
To: "Pascal Zimmer" <zimmer@easynet.fr>, <caml-list@inria.fr>
Subject: Re: Instruction return
Date: Mon, 2 Jun 1997 09:23:19 -0700
(I apologize for no French version)
> let rech x v =
> let n = vect_length v in
> for i=0 to n-1 do
> if v.(i) = x then return true
> done; false;;
This is one of the two main control problems with functional programming,
IMHO.
The solution I use is:
exception Found_it
let rech x v =
try
for i = 0 to pred (vect_length v) do
if v.(i) = x then raise Found_it
done;
false
with Found_it -> true
You don't have to assign vect_length v to n; it is only evaluated once
anyway.
If iter is defined on the type of v, then you can also use
let rech x v =
try
let f x1 = if x1 = x then raise Found_it in
iter f v; false
with Found_it -> true
The other control problem is when you want the equivalent of:
x = foo(a);
bar();
return x;
If you try
let x = foo(a) in
bar();
x
then bar gets done first, instead of second. I use this instead:
let f x = bar(); x in
in f (foo a)
I haven't found any other serious problems with Caml's logic flow. These
two just take some getting used to.
Dwight
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