[Haskell-cafe] Separate a string into a list of strings
jupdike at gmail.com
Mon Jun 12 19:34:15 EDT 2006
Funny. I have a module called Useful.hs with some of these same sorts
of functions. (coming from Python where I used .split(',') and
.replace('\r', '') and such a lot):
module Useful where
import List ( intersperse, tails )
import Numeric ( readHex )
hex2num :: (Num a) => String -> a
hex2num s = let (result, _):_ = readHex s in result
toEnv s = map tuple (split ';' s)
tuple :: String -> (String, String)
tuple line = case split '=' line of
a:b:_ -> (a,b)
a:_ -> (a,"")
_ -> ("","") -- not good, probably won't happen for my typical usage...
split :: Char -> String -> [String]
split _ "" = 
split c s = let (l, s') = break (== c) s
in l : case s' of
 -> 
(_:s'') -> split c s''
beginsWith   = True
beginsWith _  = True
beginsWith  _ = False
beginsWith (a:aa) (b:bb)
| a == b = aa `beginsWith` bb
| otherwise = False
dropping   = 
dropping  _ = 
dropping x  = x
dropping s@(a:aa) (b:bb) | a == b = dropping aa bb
| otherwise = s
-- replace all occurrences of 'this' with 'that' in the string 'str'
-- like Python replace
replace _ _  = 
replace this that str
| str `beginsWith` this = let after = (str `dropping` this)
in that ++ replace this that after
| otherwise =
let x:xs = str
in x : replace this that xs
eat s = replace s ""
-- sometimes newlines get out of hand on the end of form POST submissions,
-- so trim all the end newlines and add a single newline
fixEndingNewlines = reverse . ('\n':) . dropWhile (=='\n') . reverse .
filter (/= '\r')
endsWith a b = beginsWith (reverse a) (reverse b)
a `contains` b = any (`beginsWith` b) $ tails a
On 6/12/06, Neil Mitchell <ndmitchell at gmail.com> wrote:
> I tend to use the module TextUtil (or Util.Text) from Yhc for these
> kind of string manipulations:
> separate = splitList ","
> I am currently thinking about making this module into a standalone
> library with some other useful functions, if people have any opinions
> on this then please let me know.
> On 6/12/06, Sara Kenedy <sarakenedy at gmail.com> wrote:
> > Hi all,
> > I want to write a function to separate a string into a list of strings
> > separated by commas.
> > Example:
> > separate :: String -> [String]
> > separate "Haskell, Haskell, and Haskell" = ["Haskell", "Haskell", "and Haskell"]
> > If anyone has some ideas, please share with me. Thanks.
> > S.
> > _______________________________________________
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> > Haskell-Cafe at haskell.org
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