66089e97de
Eg, showImprecise 1 1.99 returned "1.1" rather than "2". The 9 rounded upward to 10, and that was wrongly used as the decimal, rather than carrying the 1. Sponsored-by: Jack Hill on Patreon
25 lines
803 B
Haskell
25 lines
803 B
Haskell
{- numbers for humans
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-
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- Copyright 2012-2021 Joey Hess <id@joeyh.name>
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-
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- License: BSD-2-clause
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-}
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module Utility.HumanNumber (showImprecise) where
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{- Displays a fractional value as a string with a limited number
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- of decimal digits. -}
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showImprecise :: RealFrac a => Int -> a -> String
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showImprecise precision n
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| precision == 0 || remainder' == 0 = show (round n :: Integer)
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| otherwise = show int' ++ "." ++ striptrailing0s (pad0s $ show remainder')
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where
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int :: Integer
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(int, frac) = properFraction n
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remainder = round (frac * 10 ^ precision) :: Integer
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(int', remainder')
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-- carry the 1
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| remainder == 10 ^ precision = (int + 1, 0)
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| otherwise = (int, remainder)
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pad0s s = replicate (precision - length s) '0' ++ s
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striptrailing0s = reverse . dropWhile (== '0') . reverse
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