Output an element the number of times I want

Question

I have this code:

lado ::  [([Char],Int)] -> [[Char]]
lado xs = [a | (a,b) <- xs]

I need to output this:

> lado [("A         


        

Answer 1

You can use recursion to accomplish this:

lado :: [(a, Int)] -> [a]
-- base case
lado [] = []
-- take each of the non-zero elements then recurse
lado xs = map fst nonzero ++ lado subtracted
    where
        -- find elements with non-zero count
        nonzero = filter (\x -> snd x > 0) xs
        -- subtract one from the count for each of those elements
        subtracted = map (\(x, n) -> (x, n - 1)) nonzero