CODEWITHSUNDEEP
listhaskell
Lely22
Lely22

Reputation: 19

Remove an element from a list of lists Haskell

I' am trying to remove an element from a list of lists, but only if the element is on a list with length 1. For example:

removeElement 1 [[2,3],[1,2],[1]]  
                [[2,3],[1,2]]

removeElement 2 [[1,2,3,4]] 
                [[1,2,3,4]]

removeElement 3 [[3],[1,4,5]] 
                [[1,4,5]]

So far I have this, but I don't know how to continue, or which function use.

removeElement :: (Eq a) => a -> [[a]] -> [[a]]
removeElement a [[]] = []
removeElement a ((x:xs):rs) = if a == x then (xs:rs) else  [x] :( removeElement a (xs:rs))

Upvotes: 0

Views: 1160

Answers (1)

Fabián Heredia Montiel
Fabián Heredia Montiel

Reputation: 1687

This is an example of filtering:

removeElement :: Eq a => a -> [[a]] -> [[a]]
removeElement e = filter (/= [e])

Testing your examples with ghci:

> removeElement 1 [[2,3],[1,2],[1]]
[[2,3],[1,2]]
> removeElement 2 [[1,2,3,4]]
[[1,2,3,4]]
> removeElement 3 [[3],[1,4,5]]
[[1,4,5]]

Upvotes: 3

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