Get input to [[String]] Haskell

Question

I want to get my input to be a list of lists. Each row of text has to be a list of strings and the full text will be the list of lists. How could I do this? I have this as the main:

main :: IO ()
main = interact (lines >>> foo >>> unlines)

So if this is the input:

These are random
Words of text
example example example

The result should be this:

[[These, are, random], [Words, of, text],[example, example, example]]

It is not really clear how you would convert the [String] list into a [[String]] list. Based on what condition? Do you want the "words" of that line? — willeM_ Van Onsem
– willeM_ Van Onsem, Commented Sep 17, 2017 at 16:06

willeM_ Van Onsem · Accepted Answer · 2017-09-17 16:54:11Z

1

Haskell has a function words :: String -> [String]. For example:

Prelude> words "These are random"
["These","are","random"]

Now we can do this for a list of lines by using map :: (a -> b) -> [a] -> [b]:

Prelude> map words ["These are random","Words of text","example example example"]
[["These","are","random"],["Words","of","text"],["example","example","example"]]

You can combine this with lines to extract the lines of the string first:

Prelude> (map words . lines) "These are random\nWords of text\nexample example example"
[["These","are","random"],["Words","of","text"],["example","example","example"]]

So if foo has type foo :: [[String]] -> [[String]], you can use:

main = interact (unlines . map unwords . foo . map words . lines)

edited Sep 17, 2017 at 16:54

answered Sep 17, 2017 at 16:41

willeM_ Van Onsem

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