[Haskell-cafe] Hi I need help for very simple question!

[Bryan Donlan]

Taillefer, Troy (EXP) wrote:
> Hi there
> 
> 1. First of all never forget your base case for exiting your recursion
> 2. you need to break up the problem like so
> 
> 
> import Char
> 
> -- get the first word
> word :: String -> String
> word [] = []
> word ( x : x1 : xs )
> 	| isSpace x = []
> 	| isSpace x1 = x : []
> 	| otherwise = x : x1 : word(xs)
> 
> -- get everything but the first word
> rest :: String -> String
> rest [] = []
> rest ( x : x1 : xs )
> 	| isSpace x = x1 : xs
> 	| isSpace x1 = xs
> 	| otherwise = rest(xs)
> 
> intoWords :: String -> [ String ]
> intoWords [] = []
> intoWords ws = word(ws) : words( rest(ws) ) -- glue the first word and
> call recursively on the rest

Personally, I think it's a bit clearer to use dropWhile and span:
import Data.List
import Data.Char

mywords :: String -> [String]

mywords string
     | word == ""
     = []
     | otherwise
     = word:mywords remain
     where
         (word, remain) =
             span (not . isSpace) . dropWhile isSpace $ string