開発環境
- OS X Mavericks - Apple(OS)
- BBEdit - Bare Bones Software, Inc., Emacs (Text Editor)
- Haskell (純粋関数型プログラミング言語)
- GHC (The Glasgow Haskell Compiler) (処理系)
- The Haskell Platform (インストール方法、モジュール等)
初めてのコンピュータサイエンス(Jennifer Campbell、Paul Gries、Jason Montojo、Greg Wilson(著)長尾 高弘(翻訳))の6章(条件分岐)、6.5(練習問題)、9をHaskellで解いてみる。
その他参考書籍
- プログラミングHaskell (オーム社) Graham Hutton(著) 山本 和彦(翻訳)
- Real World Haskell―実戦で学ぶ関数型言語プログラミング (オライリージャパン) Bryan O'Sullivan John Goerzen Don Stewart(著) 山下 伸夫 伊東 勝利 株式会社タイムインターメディア(翻訳)
6.5(練習問題)、9.
コード(BBEdit)
Sample.hs
{-# OPTIONS -Wall -Werror #-}
main :: IO ()
main = do
mapM_ putStr $ "Celsius ":map (++" ") units
putStrLn ""
mapM_ putStrLn $
map (\(a:b:c:d:e:f:g:h:[]) -> strFormat a 7 2 ++
' ':strFormat b 10 2 ++
' ':strFormat c 6 2 ++
' ':strFormat d 7 2 ++
' ':strFormat e 7 2 ++
' ':strFormat f 6 2 ++
' ':strFormat g 7 2 ++
' ':strFormat h 7 2) $
map (\t -> t:map (temperatures t "Celsius")
units)
[300.00, 290.00.. -260.00]
temperatures :: Double -> String -> String -> Double
temperatures t source = fromCelsius $ toCelsius t source
toCelsius :: Double -> String -> Double
toCelsius t "Kelvin" = t - 273.15
toCelsius t "Celsius" = t
toCelsius t "Fahrenheit" = (t - 32) * 5 / 9
toCelsius t "Rankine" = (t - 491.67) * 5 / 9
toCelsius t "Delisle" = 100 - t * 2 / 3
toCelsius t "Newton" = t * 100 / 33
toCelsius t "Reasumur" = t * 5 / 4
toCelsius t "Romer" = (t - 7.5) * 40 / 21
toCelsius _ s = error $ s ++"は摂氏に変換できない。"
fromCelsius :: Double -> String -> Double
fromCelsius t "Kelvin" = t + 273.15
fromCelsius t "Celsius" = t
fromCelsius t "Fahrenheit" = t * 9 / 5 + 32
fromCelsius t "Rankine" = (t + 273.15) * 9 / 5
fromCelsius t "Delisle" = (100 - t) * 3 / 2
fromCelsius t "Newton" = t * 33 / 100
fromCelsius t "Reaumur" = t * 4 / 5
fromCelsius t "Romer" = t * 21 / 40 + 7.5
fromCelsius _ s = error $ "摂氏から" ++ s ++ "に変換できない。"
units :: [String]
units = ["Fahrenheit", "Kelvin", "Rankine", "Delisle", "Newton", "Reaumur",
"Romer"]
strFormat :: Double -> Int -> Int -> String
strFormat a m n =
let s = show $ myRound a n
in replicate (m - length s) ' ' ++ s
myRound :: Double -> Int -> Double
myRound a n | a >= 0 = (fromInteger $ round $ a * 10 ^ n) / 10 ^ n
| otherwise =
-1 * (fromInteger $ round $ (abs a) * 10 ^ n / 10 ^ n)
入出力結果(Terminal, runghc)
$ runghc Sample.hs
Celsius Fahrenheit Kelvin Rankine Delisle Newton Reaumur Romer
300.0 572.0 573.15 1031.67 -300.0 99.0 240.0 165.0
290.0 554.0 563.15 1013.67 -285.0 95.7 232.0 159.75
280.0 536.0 553.15 995.67 -270.0 92.4 224.0 154.5
270.0 518.0 543.15 977.67 -255.0 89.1 216.0 149.25
260.0 500.0 533.15 959.67 -240.0 85.8 208.0 144.0
250.0 482.0 523.15 941.67 -225.0 82.5 200.0 138.75
240.0 464.0 513.15 923.67 -210.0 79.2 192.0 133.5
230.0 446.0 503.15 905.67 -195.0 75.9 184.0 128.25
220.0 428.0 493.15 887.67 -180.0 72.6 176.0 123.0
210.0 410.0 483.15 869.67 -165.0 69.3 168.0 117.75
200.0 392.0 473.15 851.67 -150.0 66.0 160.0 112.5
190.0 374.0 463.15 833.67 -135.0 62.7 152.0 107.25
180.0 356.0 453.15 815.67 -120.0 59.4 144.0 102.0
170.0 338.0 443.15 797.67 -105.0 56.1 136.0 96.75
160.0 320.0 433.15 779.67 -90.0 52.8 128.0 91.5
150.0 302.0 423.15 761.67 -75.0 49.5 120.0 86.25
140.0 284.0 413.15 743.67 -60.0 46.2 112.0 81.0
130.0 266.0 403.15 725.67 -45.0 42.9 104.0 75.75
120.0 248.0 393.15 707.67 -30.0 39.6 96.0 70.5
110.0 230.0 383.15 689.67 -15.0 36.3 88.0 65.25
100.0 212.0 373.15 671.67 0.0 33.0 80.0 60.0
90.0 194.0 363.15 653.67 15.0 29.7 72.0 54.75
80.0 176.0 353.15 635.67 30.0 26.4 64.0 49.5
70.0 158.0 343.15 617.67 45.0 23.1 56.0 44.25
60.0 140.0 333.15 599.67 60.0 19.8 48.0 39.0
50.0 122.0 323.15 581.67 75.0 16.5 40.0 33.75
40.0 104.0 313.15 563.67 90.0 13.2 32.0 28.5
30.0 86.0 303.15 545.67 105.0 9.9 24.0 23.25
20.0 68.0 293.15 527.67 120.0 6.6 16.0 18.0
10.0 50.0 283.15 509.67 135.0 3.3 8.0 12.75
0.0 32.0 273.15 491.67 150.0 0.0 0.0 7.5
-10.0 14.0 263.15 473.67 165.0 -3.0 -8.0 2.25
-20.0 -4.0 253.15 455.67 180.0 -7.0 -16.0 -3.0
-30.0 -22.0 243.15 437.67 195.0 -10.0 -24.0 -8.0
-40.0 -40.0 233.15 419.67 210.0 -13.0 -32.0 -14.0
-50.0 -58.0 223.15 401.67 225.0 -16.0 -40.0 -19.0
-60.0 -76.0 213.15 383.67 240.0 -20.0 -48.0 -24.0
-70.0 -94.0 203.15 365.67 255.0 -23.0 -56.0 -29.0
-80.0 -112.0 193.15 347.67 270.0 -26.0 -64.0 -34.0
-90.0 -130.0 183.15 329.67 285.0 -30.0 -72.0 -40.0
-100.0 -148.0 173.15 311.67 300.0 -33.0 -80.0 -45.0
-110.0 -166.0 163.15 293.67 315.0 -36.0 -88.0 -50.0
-120.0 -184.0 153.15 275.67 330.0 -40.0 -96.0 -56.0
-130.0 -202.0 143.15 257.67 345.0 -43.0 -104.0 -61.0
-140.0 -220.0 133.15 239.67 360.0 -46.0 -112.0 -66.0
-150.0 -238.0 123.15 221.67 375.0 -50.0 -120.0 -71.0
-160.0 -256.0 113.15 203.67 390.0 -53.0 -128.0 -76.0
-170.0 -274.0 103.15 185.67 405.0 -56.0 -136.0 -82.0
-180.0 -292.0 93.15 167.67 420.0 -59.0 -144.0 -87.0
-190.0 -310.0 83.15 149.67 435.0 -63.0 -152.0 -92.0
-200.0 -328.0 73.15 131.67 450.0 -66.0 -160.0 -98.0
-210.0 -346.0 63.15 113.67 465.0 -69.0 -168.0 -103.0
-220.0 -364.0 53.15 95.67 480.0 -73.0 -176.0 -108.0
-230.0 -382.0 43.15 77.67 495.0 -76.0 -184.0 -113.0
-240.0 -400.0 33.15 59.67 510.0 -79.0 -192.0 -118.0
-250.0 -418.0 23.15 41.67 525.0 -82.0 -200.0 -124.0
-260.0 -436.0 13.15 23.67 540.0 -86.0 -208.0 -129.0
$
{-# OPTIONS -Wall -Werror #-}を記述してるから、細かく型を指定(:: Double)しないと警告がいっぱい出た。慣れるまでは{-# OPTIONS -Wall -Werror #-}の記述を消さずに細かく型を指定していくことに。
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