CODEWITHSUNDEEP
algorithmhaskell
Kakalaki
Kakalaki

Reputation: 35

How do I check if a list of Bool value contain the same value?

I want to write a function like:

sameBool :: [Bool] -> Bool

for example:

[True, False, True] => False
[True, True] => True

Here's my solution:

sameBool :: [Bool] -> Bool
sameBool xs = if head xs == True
                  then length (filter (== False) xs) == 0
                  else length (filter (== True)  xs) == 0

Effective though not elegant. I'm looking for some more elegant solution.

Upvotes: 3

Views: 86

Answers (1)

Rahn
Rahn

Reputation: 5405

With all:

sameBool :: [Bool] -> Bool
sameBool xs = all (== head xs) xs

With nub from Data.List:

import Data.List

sameBool :: [Bool] -> Bool
sameBool = (== 1) . length . nub

Actually, they works for any instance of Eq:

sameBool :: Eq a => [a] -> Bool
sameBool xs = all (== head xs) xs
-- Note: return True for []

sameBool :: Eq a => [a] -> Bool
sameBool = (== 1) . length . nub
-- Note: return False for []

Check nubBy for types that aren't instances of Eq.

Upvotes: 7

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