I'm new to haskell programming and I'm trying to check if the diagonally adjacent elements in the nested lists are not negative of each other. I have my function as:
checkNegation :: [[Int]] -> Bool
Example: checkNegation[[1,2], [3, -1]] will return False
checkNegation [[1,2],[-1,3]] will return True.
I would suggest breaking the problem into steps.
Step 1: Write a function to get the diagonal elements:
diag :: [[a]] -> [a]
You may find this question helpful.
Step 2: You'd like to check if the adjacent elements of the resulting list are negatives of each other:
allAdjNeg :: [Int] -> Bool
where allAdjNeg [-1,1,-1,1] = True.
This, too, might be most easily done in steps. In step 2(a), check each pair of adjacent elements. You may be able to adapt the answer to this question to write a function:
adjNeg :: [Int] -> [Bool]
Hint: If you define a function isNeg x y = x == -y, this is a binary operator just like (-) and can be used with zipWith in the same way.
In step 2(b), you want to see if the list [Bool] returned by adjNeg is all-True. The and :: [Bool] -> Bool function will be helpful here. That should allow you to define allAdjNeg.
Then, your final function will be something like:
checkNegation :: [[Int]] -> Bool
checkNegation lsts = not (allAdjNeg (diag lsts))
