Why do I get 'variable not in scope' for Just ord <*> Nothing?

Question

I'm learning Haskell from a popular book .

It includes the following ghci command :

ghci> Just ord <*> Nothing  
Nothing

When I run this in ghci I get:

<interactive>:1:6: error:
    • Variable not in scope: ord :: a0 -> b
    • Perhaps you meant one of these:
        ‘or’ (imported from Prelude), ‘odd’ (imported from Prelude)

I think there is a typo, either due to an author mistake or the version of Haskell changing the syntax.

My question is: Why do I get variable not in scope for Just ord <*> Nothing ?

Answer 1

A quick search for "ord" on Hoogle reveals that it lives in the Data.Char module . (I have no idea whether it was always there, or whether it only recently got moved there.) So you just need to import Data.Char into your ghci session.

ghci> import Data.Char
ghci> Just ord <*> Nothing
Nothing