haskelloverridinghaskell-prelude

Is there a way to hide gcd?

I am rewriting the gcd function for an assignment, but when I'm trying to hide gcd, like so:

import Prelude hiding ((gcd))

I get the error

Parse error on input'gcd'.

I'm certain I've completed the redefinition of gcd, but I can't stop the error

Ambiguous occurrence, it could refer to 'Prelude.gcd'

unless I manage to hide gcd.

Here is my full code (apologies can't find upload file):

import Prelude hiding ((||)) 
import Prelude hiding ((gcd))

gcd :: Int -> Int -> Int
gcd x y
    | x == y    = x
    | x < y     = gcd x (y-x)
    | otherwise = gcd (x-y) y

And here is my error after changing to import Prelude hiding (gcd):

Error

Solution

  • If you want to hide multiple things from a module, you need to import it once and specify everything to hide. Importing it twice will result in each line's exclusions nullifying the other. So do this instead:

    import Prelude hiding ((||), gcd)

    (And as previously mentioned in the comments, gcd isn't an operator, so it shouldn't have parentheses around it like || does.)