Re: [Haskell-beginners] Defining 'words' in terms of 'span'

Am Dienstag 16 März 2010 18:23:33 schrieb Ozgur Akgun:

You might start with looking into span<http://haskell.org/ghc/docs/latest/html/libraries/base-4.2.0.0/Prel ude.html#v:span> .

span :: (a -> Bool) -> [a] -> ([a], [a])

And then, using span, write a function that splits the first word off a String. And a function to use when the String doesn't start with a word (like "", " made glorious summer by this son of York.", "2+3", ...).

For example try these,

span ('a'==) "abcd" span ('a'==) "aaabcd" span ('c'==) "abcd" span ('c'/=) "abcd" span ('c'/=) "abcdcdcd"

On 16 March 2010 17:08, Roger Whittaker wrote:

...

I found some exam papers linked from this page: http://www.cs.chalmers.se/Cs/Grundutb/Kurser/d1pt/d1pta/external.html

And I have been trying some questions from them.

I'm currently baffled by question 2(b) on this one: http://www.cs.chalmers.se/Cs/Grundutb/Kurser/d1pt/d1pta/tenta2000-04.p s

A word is a sequence of alphabetic characters, which you can recognise using the standard function

isAlpha :: Char -> Bool

Using span, define a function words :: String -> [String] which finds a list of the words occurring in a string. For example,

words "Now is the winter of our discontent!" == ["Now","is","the","winter","of","our","discontent"]

words "2+3" == []

words "1 by 1" == ["by"]

Can anyone give me a clue how to start?

-- ======================== Roger Whittaker roger@disruptive.org.uk http://disruptive.org.uk ======================== _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners