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We define

    properFraction (x:%y) = (fromInteger (toInteger q), r:%y)
      where (q, r) = quotRem x y

The first problem is that this produces a lazy pair. The second problem is that it uses fromInteger . toInteger rather than fromIntegral; the latter has rewrite rules that the former lacks. The whole thing should be written as

    properFraction (x:%y) = (q', r:%y)
      where !(q, r) = quotRem x y
            !q' = fromIntegral q

or possibly

    properFraction (x:%y) = (fromIntegral q, r:%y)
      where !(q, r) = quotRem x y

The latter is better if someone only wants the fractional part and is using Integral types for which fromIntegral is unusually expensive, but I don't know if that's really worth worrying about.

Trac metadata

Trac field	Value
Version	8.6.3
Type	Task
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Core Libraries
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