No, that's not possible. :: is an algebraic constructor, which means,
among other things, that it accepts no neutral element (well, except
when the list is infinite, but that's probably not what you're looking
for).

Cheers,
 David

On Sun, 2009-03-08 at 22:59 -0500, Su Zhang wrote:
> Hi all,
>  
> I have a question on ocaml, is there a way to write a empty element
> say a which can make a::ax=ax ? I tried to find out in library, yet I
> didn't get the right way out, and it doesn't work if I make a=[], so
> do you know whether there is a technique can realize this function?
> I've got stuck on this point for a very long time.
>  
> thanks
> 
> -- 
> Su Zhang
> PHD Student 
> Computer Information and Science
> Kansas State University 
> 
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-- 
David Teller-Rajchenbach
 Security of Distributed Systems
  http://www.univ-orleans.fr/lifo/Members/David.Teller
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