ciol wrote:

> after factoring common prefixes, the author obtains :
> 
> Expr ::= Mult RestExpr
> 
> RestExpr ::= + Mult RestExpr
>             |- Mult RestEXpr
>             |(* nothing *)
> 
> [...]
> 
> But I don't obtain the same result for RestExpr :
> 
> RestExpr ::= + Mult Expr
>             |- Mult Expr
>             | (* nothing *)
> 

_Sorry_, it's an error, I obtain :
RestExpr ::= + Expr
            | - Expr
            | (* nothing *)

But I've just realized that the author's solution is in fact the same as 
mine (he replaced Expr in RestExpr by Mult RestExpr. But why ? Isn't it 
more complicated ? The result in caml will be identical  wont it be ?