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!"

这段代码给我一个错误,"在输入上解析错误'=>'"我不知道为什么.有帮助吗？谢谢 !

Answer 1

这条线:

bmiTell :: => Double -> String

具有符号=>,用于从包含约束类型的签名中分离出类约束.但是,你没有任何约束,没有任何限制Show a =>.解决方案？删除它!

bmiTell :: Double -> String