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Date: Fri, 20 Jan 2012 10:11:51 +0100
From: Jerome Vouillon <vouillon@pps.jussieu.fr>
To: Sebastien Ferre <Sebastien.Ferre@irisa.fr>
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Subject: Re: [Caml-list] is there a more concise way to write this?

On Fri, Jan 20, 2012 at 09:37:17AM +0100, Sebastien Ferre wrote:
> You can make it even more concise by defining a helping function.
> 
> let b2l b x = if b then [x] else [];;
> 
> let a =
>   b2l out o @
>   b2l value v;;

You can also include the list concatenation in the helper function:

    let maybe b v c = if b then v :: c else c
    let g out o value v = maybe out o (maybe value v [])

And the parentheses can be avoided by using a right associative
application operator:

    let (@@) f x = f x
    let a = maybe out o @@ maybe value v @@ []

-- Jerome