29 lines
872 B
Haskell
29 lines
872 B
Haskell
import Data.Ratio
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import Text.Printf (PrintfType, printf)
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-- Map a value from the range [a1,a2] to the range [b1,b2]. We don't check
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-- for empty ranges.
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mapRange
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:: Fractional a
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=> (a, a) -> (a, a) -> a -> a
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mapRange (a1, a2) (b1, b2) s = b1 + (s - a1) * (b2 - b1) / (a2 - a1)
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main :: IO ()
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main
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-- Perform the mapping over floating point numbers.
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= do
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putStrLn "---------- Floating point ----------"
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mapM_ (\n -> prtD n . mapRange (0, 10) (-1, 0) $ fromIntegral n) [0 .. 10]
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-- Perform the same mapping over exact rationals.
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putStrLn "---------- Rationals ----------"
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mapM_ (\n -> prtR n . mapRange (0, 10) (-1, 0) $ n % 1) [0 .. 10]
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where
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prtD
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:: PrintfType r
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=> Integer -> Double -> r
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prtD = printf "%2d -> %6.3f\n"
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prtR
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:: PrintfType r
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=> Integer -> Rational -> r
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prtR n x = printf "%2d -> %s\n" n (show x)
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