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edsko/doubleToFixed.hs

Last active February 12, 2019 11:51
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doubleToFixed.hs
-- | Convert 'Double' to fixed precision
--
-- For precision 'E1', we have
--
-- > 1.000 1.010 1.040 1.049 1.050 1.051 1.090 1.100
-- > floor | 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.1
-- > round | 1.0 1.0 1.0 1.0 1.0(*) 1.1 1.1 1.1
-- > ceiling | 1.0 1.1 1.1 1.1 1.1 1.1 1.1 1.1
--
-- (*): See <https://en.wikipedia.org/wiki/IEEE_754#Rounding_rules>
doubleToFixed :: forall a. HasResolution a
=> (Double -> Integer) -- ^ Rounding policy
-> Double -> Fixed a
doubleToFixed r d = MkFixed $ r (d * fromIntegral (resolution (Proxy @a)))
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