GitLab

Currently, it's defined

stringify :: String -> String
stringify s = reverse .  dropWhile isSpace . reverse -- drop trailing space
              . dropWhile isSpace                    -- drop leading space
              . compressSpaces                       -- replace each span of
                                                     -- whitespace with a single space
              $ s
    where compressSpaces [] = []
          compressSpaces (a:as) | isSpace a = ' ' : compressSpaces (dropWhile isSpace as)
          compressSpaces (a:as) = a : compressSpaces as

If we're going to go to the trouble of doing this by hand, we might as well take the efficiency advantage doing so can give us:

stringify :: String -> String
-- Spec: stringify = unwords . words
stringify xs = go False (dropWhile isSpace xs)
  where
    go _haveSpace [] = []
    go  haveSpace (x:xs)
      | isSpace x = go True xs
      | otherwise = if haveSpace
                    then ' ' : x : go False xs
                    else x : go False xs

Trac metadata

Trac field	Value
Version	7.9
Type	Task
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Code Coverage
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture