Re: Instruction return

From: Dwight VandenBerghe (
Date: Mon Jun 02 1997 - 18:23:19 MET DST

Message-Id: <>
From: "Dwight VandenBerghe" <>
To: "Pascal Zimmer" <>, <>
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,
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.


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