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Re: Instruction return
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Date: 1997-06-02 (21:20)
From: Dwight VandenBerghe <dwight@p...>
Subject: Re: Instruction return
(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,
The solution I use is:

	exception Found_it   
	let rech x v =
	        for i = 0 to pred (vect_length v) do
	            if v.(i) = x then raise Found_it
	    with Found_it -> true
You don't have to assign vect_length v to n; it is only evaluated once
If iter is defined on the type of v, then you can also use

	let rech x v =
	        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);
    return x;

If you try 

    let x = foo(a) in

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.