How do I split a list of tuples into two lists in haskell using the map function?
dictionary, haskell, unzip
Solution
Well, `map :: (a -> b) -> ([a] -> [b])` returns a list, right? And you want your function to return two lists, so... you'll need to use `map` twice. Here's a skeleton for you to fill in:
unzip xs = (map {- ??? -} xs, map {- ??? -} xs)
Unfortunately, insisting on using `map` is inefficient, because it means you must make two passes over the list. You can do a bit better, but it's tricky! Give it a shot, then see how well you did by comparing it with GHC's implementation.
Problem
This is for homework due yesterday but I do not want the answer just a point to the right direction please;) I am trying to implement the `unzip` function using `map` and lambda with haskell. ``` :t unzip [(a,b)] -> ([a],[b]) ``` and so I am thinking that the lambda would look like `\(a,b)->([a],[b])` and that sort of works except I am getting from my input of `[(4,5),(7,5),(9,7)] => [([4],[5]),([7],[5]),([9],[7])]` but I would have liked to have seen `[4,7,9],[5,5,7]`. So what am I doing wrong here? Thanks in advance for pointing me in the right direction