[project @ 2003-08-19 16:39:13 by simonmar]

[ghc-base.git] / Data / List.hs

diff --git a/Data/List.hs b/Data/List.hs
index da58031..0a4bb20 100644 (file)
--- a/Data/List.hs
+++ b/Data/List.hs
@@ -141,12 +141,12 @@ import Prelude hiding (Maybe(..))
 #endif
 
 import Data.Maybe
+import Data.Char       ( isSpace )
 
 #ifdef __GLASGOW_HASKELL__
 import GHC.Num
 import GHC.Real
 import GHC.List
-import GHC.Show        ( lines, words, unlines, unwords )
 import GHC.Base
 #endif
 
@@ -520,7 +520,7 @@ deleteFirstsBy eq       =  foldl (flip (deleteBy eq))
 -- | The 'group' function takes a list and returns a list of lists such
 -- that the concatenation of the result is equal to the argument.  Moreover,
 -- each sublist in the result contains only equal elements.  For example,
--- when applied to the string `Mississippi', the result is @["M","i","ss","i","ss","i","pp","i"]@.
+-- when applied to the string \"Mississippi\", the result is @[\"M\",\"i\",\"ss\",\"i\",\"ss\",\"i\",\"pp\",\"i\"]@.
 group                   :: (Eq a) => [a] -> [[a]]
 group                   =  groupBy (==)
 
@@ -723,3 +723,49 @@ product    l       = prod l 1
     prod (x:xs) a = prod xs (a*x)
 #endif
 #endif  /* __GLASGOW_HASKELL__ */
+
+-- -----------------------------------------------------------------------------
+-- Functions on strings
+
+-- lines breaks a string up into a list of strings at newline characters.
+-- The resulting strings do not contain newlines.  Similary, words
+-- breaks a string up into a list of words, which were delimited by
+-- white space.  unlines and unwords are the inverse operations.
+-- unlines joins lines with terminating newlines, and unwords joins
+-- words with separating spaces.
+
+lines                  :: String -> [String]
+lines ""               =  []
+lines s                        =  let (l, s') = break (== '\n') s
+                          in  l : case s' of
+                                       []      -> []
+                                       (_:s'') -> lines s''
+
+unlines                        :: [String] -> String
+#ifdef USE_REPORT_PRELUDE
+unlines                        =  concatMap (++ "\n")
+#else
+-- HBC version (stolen)
+-- here's a more efficient version
+unlines [] = []
+unlines (l:ls) = l ++ '\n' : unlines ls
+#endif
+
+words                  :: String -> [String]
+words s                        =  case dropWhile {-partain:Char.-}isSpace s of
+                               "" -> []
+                               s' -> w : words s''
+                                     where (w, s'') = 
+                                             break {-partain:Char.-}isSpace s'
+
+unwords                        :: [String] -> String
+#ifdef USE_REPORT_PRELUDE
+unwords []             =  ""
+unwords ws             =  foldr1 (\w s -> w ++ ' ':s) ws
+#else
+-- HBC version (stolen)
+-- here's a more efficient version
+unwords []             =  ""
+unwords [w]            = w
+unwords (w:ws)         = w ++ ' ' : unwords ws
+#endif