[Haskell-cafe] Re: ANN: weighted-regexp-0.1.0.0

[Sebastian Fischer]

On Jul 27, 2010, at 9:15 AM, Sjoerd Visscher wrote:

> Oh, by the way, with noMatch, eps, alt and seq_ RegExp is itself a  
> Semiring,

Yes, but it's hard to define an Eq instance for arbitrary regular  
expressions that reflects equivalence of regexps.

There is currently only `instance Eq (RegExp Char)` which implements  
structural identity used for the QuickCheck tests.

> but I'm not sure what that would do.

I think matching a regular expression against a word in the "regular  
expressions semiring" returns an unfolding of the original regular  
expression which matches exactly the given word.

Sebastian


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