问Haskell中字符串到Morse码的转换
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Stack Overflow用户

提问于 2020-11-13 13:29:33

回答 1查看 247关注 0票数 0

data Unit = Noise | Silent deriving (Eq, Show)

type MorseCode = [Unit]

short, long, smallGap, longGap :: MorseCode
short = [Noise, Silent]
long = [Noise, Noise, Noise, Silent]
smallGap = replicate (3-1) Silent
longGap = replicate (7-1) Silent

morse :: Char -> MorseCode
morse '0' = long ++ long ++ long ++ long ++ long
morse '1' = short ++ long ++ long ++ long ++ long
morse '2' = short ++ short ++ long ++ long ++ long
morse '3' = short ++ short ++ short ++ long ++ long
morse '4' = short ++ short ++ short ++ short ++ long
morse '5' = short ++ short ++ short ++ short ++ short
morse '6' = long ++ short ++ short ++ short ++ short
morse '7' = long ++ long ++ short ++ short ++ short
morse '8' = long ++ long ++ long ++ short ++ short
morse '9' = long ++ long ++ long ++ long ++ short
morse 'A' = short ++ long
morse 'B' = long ++ short ++ short ++ short
morse 'C' = long ++ short ++ long ++ short
morse 'D' = long ++ short ++ short
morse 'E' = short
morse 'F' = short ++ short ++ long ++ short
morse 'G' = long ++ long ++ short
morse 'H' = short ++ short ++ short ++ short
morse 'I' = short ++ short
morse 'J' = short ++ long ++ long ++ long
morse 'K' = long ++ short ++ long
morse 'L' = short ++ long ++ short ++ short
morse 'M' = long ++ long
morse 'N' = long ++ short
morse 'O' = long ++ long ++ long
morse 'P' = short ++ long ++ long ++ short
morse 'Q' = long ++ long ++ short ++ long
morse 'R' = short ++ long ++ short
morse 'S' = short ++ short ++ short
morse 'T' = long
morse 'U' = short ++ short ++ long
morse 'V' = short ++ short ++ short ++ long
morse 'W' = short ++ long ++ long
morse 'X' = long ++ short ++ short ++ long
morse 'Y' = long ++ short ++ long ++ long
morse 'Z' = long ++ long ++ short ++ short
morse _ = undefined -- Avoid warnings

type Table = [(Char, MorseCode)]

morseTable :: Table
morseTable = [ (c , morse c) | c <- ['A'..'Z']++['0'..'9'] ]

所以我想要创建这个函数

convertStringToMorse :: Table -> String -> MorseCode

我试图使这个函数以一种更一般的方式工作，所以它适用于具有不同表的其他类型的代码。另外，我希望输出在每个字符之间有一个smallGap (三个silent)。

所以

convertStringToMorse morseTable "SKY" =  [Noise, Silent, Noise, Silent, Noise, Silent, Silent, Silent, Noise, Noise, Noise, Silent, Noise, Silent, Noise, Noise, Noise, Silent, Silent, Silent, Noise, Noise, Noise, Silent, Noise, Silent, Noise, Noise, Noise, Silent, Noise, Noise, Noise, Silent]

convertStringToMorse morseTable "Q" = [Noise, Noise, Noise, Silent, Noise, Noise, Noise, Silent, Noise, Silent, Noise, Noise, Noise, Silent]

convertStringToMorse morseTable ""= []

我不太确定在Haskell这样的函数会从哪里开始。

haskell

回答 1

Stack Overflow用户

发布于 2020-11-13 13:41:07

您可以使用intercalate和lookup来完成这一任务：

import Data.List

convertStringToMorse :: [(Char, MorseCode)] -> String -> Maybe MorseCode
convertStringToMorse table str = intercalate [Silent, Silent, Silent]
    <$> mapM (\x -> lookup x table) str

mapM将把[Maybe MorseCode]转换为Maybe [MorseCode]，而<$>则将intercalate函数应用到Maybe的内部。如果你对此感到困惑，请看这里。如果您确实需要一个MorseCode而不是Maybe MorseCode，您可以导入Data.Maybe并将整个函数包装在fromJust中。

票数 2

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/64821811

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