You can also do something like this instead of the case statement (this is using GHCI).  

Prelude> let exclude = ['a', 'e', 'i', 'o', 'u']

Prelude> let f excl letter | letter `elem` excl = 'x' | otherwise = letter

Prelude> map (f exclude) "hello"

"hxllx"

Rob Ziemba

On Sun, Oct 4, 2009 at 9:10 AM, Colin Paul Adams <colin@colina.demon.co.uk> wrote:

>>>>> "John" == John Moore <john.moore54@gmail.com> writes:

   John> Hi, I am now writing a function that replaces vowels with
   John> the letter x.  eg.put in a string "help" and out comes hxlp.
   John> I tried this:

   John> f x = case x of

   John>       {'a' -> 'x';'e' -> 'x';'i' -> 'x';'o' -> 'x';'u' ->
   John> 'x';_ -> x}

   John> but this wont work on strings, only on the individual
   John> letters. Any direction would be very welcome.

You need to call

map f "whatever"

where f is your function for replacing a character (as above).
--
Colin Adams
Preston Lancashire
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