Roelof Wobben schreef op 6-2-2015 om 10:25:

Hello,

I have figured out how I can make from 123 [1,2,3]

I did it this way :

-- | convert a number to a array in pieces where a negative number will be a empty array. toDigits :: Integer -> [Integer] toDigits n | n <= 0 = [] | otherwise = toDigits (n `div` 10) ++ [n `mod` 10]

but now when I do toDigits 0 , I see [] as output where I was expected [0]

But when I do toDigits 100 I see the right output [ 1,0,0] which surprises me because I tought that with the first 0 there will be a []

Or is the n the second time [0,0] and the thirth time [0] So it will be like this :

toDigits 100

to Digits [1] ++ [ 0,0] toDigits [1] ++ [0] ++ [0]

which leads to [1,0,0]

Roelof

Hmm, this is also not working : -- | convert a number to a array in pieces where a negative number will be a empty array. toDigits :: Integer -> [Integer] toDigits 0 = [0] toDigits n | n < 0 = [] | otherwise = toDigits (n `div` 10) ++ [n `mod` 10] -- | convert a number to a reversed array where a negative number will be a empty array toDigitsRev :: Integer -> [Integer] toDigitsRev 0 = [0] toDigitsRev n | n <= 0 = [] | otherwise = n `mod` 10 : toDigitsRev (n `div` 10) -- | The main entry point. main :: IO () main = do print $ toDigits 100 print $ toDigitsRev 100 print $ toDigits 0 print $ toDigitsRev 0 print $ toDigits (-17) print $ toDigitsRev (-17) you get a zero too much when you use a number above 0 .