Haskell List of tuples to list?

Question

Is it possible to convert a list of tuples [(Int,Int)] as a generic way which valid to any input size ? .. i saw in various questions thats its not possible gen

Answer 1

Your question is not very certain about how the tuples should be converted into a list. I assume that you want to have them flattend - for instance, [(1,2),(3,4)] should become [1,2,3,4].

This translation is only possible, if the two elements of your tuple are of the same type. In this case you can do something like this:

tupleToList :: [(a,a)] -> [a]
tupleToList ((a,b):xs) = a : b : tupleToList xs
tupleToList _          = []

In the general case, such a translation is impossible. One thing I could imagine to make the impossible possible is to use Either to wrap up the two different types:

tupleToList :: [(a,b)] -> [Either a b]
tupleToList ((a,b):xs) = Left a : Right b : tupleToList xs