[Haskell-cafe] Re: Fractional/negative fixity?

Lennart Augustsson lennart at augustsson.net
Tue Nov 7 17:32:39 EST 2006

On Nov 7, 2006, at 11:47 , apfelmus at quantentunnel.de wrote:

> Henning Thielemann wrote:
>> On Tue, 7 Nov 2006, Simon Marlow wrote:
>>> I'd support fractional and negative fixity.  It's a simple change to
>>> make, but we also have to adopt
>>> http://hackage.haskell.org/cgi-bin/haskell-prime/trac.cgi/wiki/ 
>>> FixityResolution
>>> I've added the proposal to the end of that page.  In fact, the page
>>> already mentioned that we could generalise fixity levels, but it  
>>> didn't
>>> mention fractional or negative values being allowed.
>> Maybe that page could also mention earlier proposals and the  
>> solutions
>> without precedence numbers. I prefer the non-numeric approach with  
>> rules
>> like "(<) binds more tightly than (&&)", because it says what is  
>> intended
>> and it allows to make things unrelated that are unrelated, e.g. infix
>> operators from different libraries. Consequently a precedence  
>> relation to
>> general infix operators like ($) and (.) had be defined in each  
>> library.
> I think that computable real fixity levels are useful, too. A further
> step to complex numbers is not advised because those cannot be  
> ordered.

But ordering of the computable reals is not computable.  So it could  
cause the compiler to loop during parsing. :)

	-- Lennart

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