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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
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(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