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Add warnings about large exponents to Real and RealFrac #107

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Add warnings about large exponents to Real and RealFrac #107

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8 changes: 6 additions & 2 deletions src/Data/Scientific/Internal.hs
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Expand Up @@ -249,7 +249,9 @@ instance Num Scientific where
-- Avoid applying 'toRational' (or 'realToFrac') to scientific numbers
-- coming from an untrusted source and use 'toRealFloat' instead. The
-- latter guards against excessive space usage.
instance Real Scientific where
instance
{-# WARNING "Inefficient for large exponents, can fill up all space and crash your program!" #-}
Real Scientific where
toRational (Scientific c e)
| e < 0 = c % magnitude (-e)
| otherwise = (c * magnitude e) % 1
Expand Down Expand Up @@ -503,7 +505,9 @@ toRationalRepetend s r
-- magnitude @10^e@. If applied to a huge exponent this could take a long
-- time. Even worse, when the destination type is unbounded (i.e. 'Integer') it
-- could fill up all space and crash your program!
instance RealFrac Scientific where
instance
{-# WARNING "Inefficient for large exponents, can fill up all space and crash your program!" #-}
RealFrac Scientific where
-- | The function 'properFraction' takes a Scientific number @s@
-- and returns a pair @(n,f)@ such that @s = n+f@, and:
--
Expand Down