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[Caml-list] mystified by typing of optional arguments

Francois Rouaix
- Francois Thomasset
- Ville-Pertti Keinonen
- Eric C. Cooper
- Jacques Carette
- Jacques Garrigue

Date:	-- (:)
From:	Eric C. Cooper <ecc@c...>
Subject:	Re: [Caml-list] mystified by typing of optional arguments

On Thu, Apr 03, 2003 at 04:50:44PM +0200, Francois Rouaix wrote:
> The following example mystifies me
> 
> let f ?opt x =
>   match opt with
>   | None -> x
>   | Some dx -> x + dx
> 
> let g x = x + 1
> 
> let h1 = function
>   | 0 -> [g]
>   | _ -> [f; g]
> 
> 
> let h2 = function
>   | _ -> [f; g]
> 
> 
> h1 is typable but not h2.
> Why is that ?

Even simpler: [g; f] type-checks, but [f; g] does not.

-- 
Eric C. Cooper          e c c @ c m u . e d u

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