I will be updating this as I go… but see also the Wikipedia page on string functions in various languages.
Joining a string list
-- Python: ",".join(lst)
-- either...
import Data.List
intercalate "," lst
-- or...
import Data.List
concat (intersperse "," lst)
Splitting on a string
-- a.split(ss)
-- You might need to get Data.List.Split from Cabal
import Data.List.Split
splitOn ss a
-- using regexes
import Text.Regex
splitRegex (mkRegex ss) a
Does the string start with the prefix?
-- Python: a.startswith(b)
import Data.List
isPrefixOf b a
-- ByteString
import Data.ByteString
isPrefixOf b a
Does the string end with the suffix?
-- Python: a.endswith(b)
import Data.List
isSuffixOf b a
-- ByteString
import Data.ByteString
isSuffixOf b a
Does one string contain another?
-- Python: a.find(b) != -1
import Data.List
isInfixOf b a
-- ByteString
import Data.ByteString
isInfixOf b a
-- ByteString
import Data.ByteString
findSubstring b a -- returns Just int or Nothing
Reverse a string
-- Python: a[::-1]
reverse a
-- ByteString
import Data.ByteString
reverse bs
Access one character
-- Python: a[pos]
a !! pos -- slow O(n)
-- ByteString
import Data.ByteString
index a pos
Where does one string contain another?
-- Python: a.find(b)
import Data.ByteString
findSubstring a b
Replace substrings
-- Python: b = a.replace(src,dest)
import Text.Regex
b = subRegex (mkRegex src) a dest
Replace regex, calling function on substitution
-- Python: b = re.sub("[0-9]+", lambda x: str(int(x.group(0)) + 1), a)
import Text.Regex (matchRegexAll, mkRegex)
subRegexFn fn re s = concat $ reverse $ sub s []
where sub s accum = case matchRegexAll re s of
Nothing -> s:accum
Just (pre, mid, post, _) -> sub post $ (fn mid):pre:accum
b = subRegexFn (read . (+ 1) . show) "[0-9]+" a
Strip leading/trailing spaces
-- Python: a.strip()
import Data.Char (isSpace)
trim :: String -> String
trim = f . f
where f = reverse . dropWhile isSpace
Loop through every line in stdin
-- Python: loop through every line in stdin, applying a function
-- for line in sys.stdin:
-- print fn(line)
let main = interact (unlines . map fn . lines)
-- or...
let main = do { a <- stdin; mapM_ print (map fn (lines a)); }
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