Haskell error parse error on input `='

Question

I\'m new to Haskell and after starting ghci I tried:

f x = 2 * x

and I obtained:

:1:4: pars         


        

Answer 1

When you type into a Haskell source file,

f x = 2 * x

is correct.

When you type directly into ghci, you need to type let at the start of the line:

let f x = 2 * x