There are many ways to do this, but since you mention you’re a Haskell beginner, a list comprehension may be easiest to understand (I’m assuming this is homework, so you have to implement it yourself, not use elemIndices): stringCount str ch = [ y | (x, y) <- zip str [0..], x == ch ] … Read more
main = do nStr <- getLine let n = read nStr print . take n $ map (^2) [1..] Stack overflow is inappropriate for questions that have not been well-researched. Hit LYAH, RWH, the Haskell wikibook, or a combination of the two before you post here. solved How can I calculate a power of 1..n … Read more
a -> b is the function type. It describes a function that takes a type a and returns a type b. >>= is the monadic bind function. It is of type Monad m => m a -> (a -> m b) -> m b. If you need to understand this, I recommend reading Learn You … Read more
Well since you got it working without the starting/ending point. An easy way to complete would be use your function but add the starting/ending point in the list in an inner function. So your interface is still same. Another way using recursion, pattern matching and guards is: — assuming the inputs to be int as … Read more
You have a constant for what the scoring is scoring :: [Int] scoring = [25, 18, 15, 12, 10, 8, 6, 4, 2, 1] Then you need a way for pairing up a driver with the score they got. Whenever you’re pairing two things in Haskell, the canonical choice is to use a tuple. The … Read more
This would be a complete implementation in Haskell import Data.List.Split (chunksOf) import Data.List import Data.Char (digitToInt) main :: IO () main = do digits <- map digitToInt <$> readFile “pifile.txt” let summator = foldl1′ (zipWith (+)) . chunksOf 4 print $ summator digits I will update this with some explanation later this day. Update @Comments … Read more
I think you may be confusing type variables which are used in type annotations, and the actual values being passed to the function. In your definition of mygcd: mygcd c = a + b Unless a and b are defined elsewhere, this will be an error. In other words, these a, b, and c are … Read more
Is the implementation of “ based on `fmap` special to Maybe applicative or can it be generalized to other applicatives? solved Is the implementation of “ based on `fmap` special to Maybe applicative or can it be generalized to other applicatives?
It can be done: composeApplicative p q = (.) <$> p <*> q For more information, read the documentation for Applicative functors, more specifically, the composition law. It is effectively a statement that any Applicative instance, composeApplicative f g <*> x must always be equal to f <*> (g <*> x). As a minor technical … Read more
You can use nested replicate :: Int -> a -> [a]: makeBoard :: Num a => Int -> Int -> [[a]] makeBoard h w = replicate h $ replicate w 1 replicate takes thus an Int and an element a and generates a list [a] that contains n times that element. So the second replicate … Read more
You would want to write a recursive function to do this. For each Tree constructor, you’ll need a different case in your function. To start with, you know that the depth of any Leaf is 1, so maxDepth :: Tree -> Int maxDepth (Leaf _) = 1 maxDepth (Branch2 c left right) = maximum [???] … Read more
additionally you want to separate the bmi-calculator from the main function as it is a pure function without any side-effects main :: IO () main = do putStrLn “Please Input your weight” w <- getLine let weight = read w :: Float putStrLn “Please Input your height” h <- getLine let height = read h … Read more
Edit: Another version suggested by David Young is findIndicesIn xs ys = findIndices (`elem` ys) xs which I prefer to my solution below. If I understand correctly, you have two lists. Call them xs and ys. You want to find the index in xs of each element in ys. You don’t mention what you want … Read more
printList :: IO () printList = do putStrLn “Printed Combined List” zip [NameList][PriorityList] There are many things wrong with this code. The parse error you are seeing is because the do block is not properly aligned. The zip on the last line must line up with the putStrLn on the line before. So either printList … Read more
You can implement it using mapM_/traverse_ or the flipped argument versions: forM_/for_. I prefer for_ since it looks more like the “enhanced for-loop” from languages like Java. import Data.Foldable (for_) myPutStr :: [(Double,String)] -> IO () myPutStr vals = do for_ vals $ \(num, str) -> do putStr str putStr “: ” print (num * … Read more