haskell - 在 haskell 中，结合 "case"和 ">>="

Question

我有很多风格的代码:

do
  x <- getSomething
  case x of
    this -> ...
    that -> ...
    other -> ...

我有什么方法可以结合“x <- ...”和“case x of”行来消除对变量的需求？

Answer 1

您可以使用绑定(bind)运算符 >>= 管道 x .

import System.Environment (getArgs)

main :: IO ()
main = getArgs >>= process
    where process ["xxx"] = putStrLn "You entered xxx"
          process ["yyy"] = putStrLn "You entered yyy"
          process _       = putStrLn "Error"