Prelude> :{
Prelude| let  bmiTell :: Double -> Double -> String
Prelude| bmiTell weight height
Prelude|   weight / height ^ 2 <= 18.5 = "You're underweight, you emo, you!"
Prelude|   weight / height ^ 2 <= 25.0 = "You're supposedly normal. Pffft, I bet you're ugly!"
Prelude|   weight / height ^ 2 <= 30.0 = "You're fat! Lose some weight, fatty!"
Prelude|   otherwise = "You're a whale, congratulations!"
Prelude| :}

<interactive>:19:1: parse error on input `bmiTell'

Prelude> :{
Prelude| let bmiTell :: Double -> Double -> String
Prelude| bmiTell weight height = undefined
Prelude| :}

<interactive>:6:1: parse error on input `bmiTell'
Prelude> :{
Prelude| let bmiTell :: Double -> Double -> String
Prelude|     bmiTell weight height = undefined
Prelude| :}
Prelude>

weight / height ^ 2

| weight / height ^ 2