Haskell：如何使用案例功能

Question

我是Haskell的新手。 我在这里有一个问题。我可以像这样的守卫做任务

task2 x "Celsius" 
   | x>=20 = "It is Hot"
   | x<= (-5) = "It is very cold"
   | x<=10 = "It is cold"
   | x<20 = "It is warm"

如何使用案例功能来完成这项任务？

喜欢

案例x＆＃34; Celsius＆＃34; = x的情况x＆gt; = 20，但它不起作用。

Answer 1

您可以将警卫放入case这样的表达式中：

case some_expression of
    x | x>=20 -> "It is Hot"
      | x<= (-5) -> "It is very cold"
      ....