Publicly exported pattern synonym for Ratios?

[andrew.lelechenko at gmail.com]

Hi,

Could you please explain, why numerator and denominator add an extra layer of laziness?

Best regards,
Andrew

> 17 сент. 2019 г., в 15:54, Zemyla <zemyla at gmail.com> написал(а):
> 
> 
> Using the numerator and denominator functions in Data.Ratio adds an extra layer of laziness to functions that have to work with Ratios (especially Rationals). I think it'd be convenient if there were a pattern synonym exported from the safe Data.Ratio:
> 
> pattern n :% d <- (n GHC.Ratio.:% d) where
>   n :% d = n % d
> 
> This way, destructuring is as fast as if you were to import GHC.Ratio directly, but it can't be used to create invalid Ratios.
> 
> The only disadvantage is that using the :% to destructure it requires an Integral constraint on the value, but 99% of the time, the value will be Integer anyway, and even in the remaining 1% you still can't construct a Ratio a without an Integral a constraint in safe code anyway, so it shouldn't matter.
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