Re: The rewrite rules matter

Surely f-star will match an empty string, by its second alternative…

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> On 25 Aug 2022, at 19:28, Bethan Tovey-Walsh <accounts@bethan.wales> wrote:
> 
> 
>> 
>> f* ⇒ f-star
>> -f-star= f, f-star|().
> 
> Maybe I’m misunderstanding something, but that would seem to require that you match at least one f? So wouldn’t this give you a rewrite of f+, not f*?
> 
> BTW
> 
>>> On 25 Aug 2022, at 15:42, John Lumley <john@saxonica.com> wrote:
>>> 
>> 
>> On 21/08/2022 18:04, Norm Tovey-Walsh wrote:
>>> f* ⇒ f-star
>>> -f-star = f+ | ().
>> I think there's a cheaper possibility for rewriting f*, which is self-contained and avoids an f+ rewrite. I seem to have been using for some time, without perhaps realising it:
>> 
>> f* ⇒ f-star
>> -f-star= f, f-star|().
>> -- 
>> John Lumley MA PhD CEng FIEE
>> john@saxonica.com