In Haskell,

I want to write a code for a function 'Func1', which returns a list that each element is multiplied by 10 when the element is negative.

The 'Func1' should use 'either' and 'map' functions.

ex. Func1 [1, -3, 4, -9] = [1, -30, 4, -90]

I wrote the code.

But, It shows an error at the 'Left x'. I don't know how to fix it.

Func1 :: (Ord a, Num a) => [a] -> [a]

Func1 [] = []

Func1 (x:xs) =

let f = either (\l -> if l < 0 then (10*) else l) id

in map (f (Left x)) (x:xs)