haskell - 在 Haskell 上输入“=>”时出现解析错误

Question

bmiTell :: => Double -> String
bmiTell bmi
    | bmi <= 18.5 = "You're underweight, you emo, you!"
    | bmi <= 25.0 = "You're supposeldly normal. Pffft, I bet you're ugly!"
    | bmi <= 30.0 = "You're fat! Lose some weight, fatty!"
    | otherwise   = "You are a whale, congratulations!"

这段代码给了我一个错误，“输入'=>'时解析错误”我不知道为什么。有什么帮助吗？谢谢你 ！

Answer 1

该行：

bmiTell :: => Double -> String

具有符号=>，用于将类约束与包含约束类型的签名分开。但是，您没有任何限制，例如Show a =>. 解决方案？删除它！

bmiTell :: Double -> String