[Haskell-cafe] Showing Data.Ratio - different on GHC vs Hugs/Yhc
Twan van Laarhoven
twanvl at gmail.com
Fri Nov 16 20:55:40 EST 2007
Neil Mitchell wrote:
> Under Hugs and Yhc, showing a Ratio 1%2 gives "1 % 2". Under GHC
> showing 1%2 gives "1%2". Does the standard say anything about this? Is
> someone wrong?
Yes, ghc is wrong here, the Haskell 98 report  specifies:
instance (Integral a) => Show (Ratio a) where
showsPrec p (x:%y) = showParen (p > ratPrec)
(showsPrec (ratPrec+1) x .
showString " % " .
showsPrec (ratPrec+1) y)
While it doesn't really matter, it is a deviation from the standard.
I would personally prefer it if rationals were shown as "1%2", because
the space is not needed, and other show instances such as lists don't
insert spaces either.
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