GF/src is now for 2.9, and the new sources are in src-3.0 - keep it this way until the release of GF 3

src-3.0/GF/Infra/PrintClass.hs

@@ -0,0 +1,51 @@
+module GF.Infra.PrintClass where
+
+import Data.List (intersperse)
+
+class Print a where
+    prt :: a -> String
+    prtList :: [a] -> String
+    prtList as = "[" ++ prtSep "," as ++ "]"
+
+prtSep :: Print a => String -> [a] -> String
+prtSep sep = concat . intersperse sep . map prt
+
+prtBefore :: Print a => String -> [a] -> String
+prtBefore before = prtBeforeAfter before ""
+
+prtAfter :: Print a => String -> [a] -> String
+prtAfter after = prtBeforeAfter "" after
+
+prtBeforeAfter :: Print a => String -> String -> [a] -> String
+prtBeforeAfter before after as = concat [ before ++ prt a ++ after | a <- as ]
+
+prtPairList :: (Print a, Print b) => String -> String -> [(a,b)] -> String
+prtPairList comma sep xys = prtSep sep [ prt x ++ comma ++ prt y | (x,y) <- xys ]
+prIO :: Print a => a -> IO ()
+prIO = putStr . prt
+
+instance Print a => Print [a] where
+    prt = prtList
+
+instance (Print a, Print b) => Print (a, b) where
+    prt (a, b) = "(" ++ prt a ++ "," ++ prt b ++ ")"
+
+instance (Print a, Print b, Print c) => Print (a, b, c) where
+    prt (a, b, c) = "(" ++ prt a ++ "," ++ prt b ++ "," ++ prt c ++ ")"
+
+instance (Print a, Print b, Print c, Print d) => Print (a, b, c, d) where
+    prt (a, b, c, d) = "(" ++ prt a ++ "," ++ prt b ++ "," ++ prt c ++ "," ++ prt d ++ ")"
+
+instance Print Char where
+    prt = return
+    prtList = id
+
+instance Print Int where
+    prt = show
+
+instance Print Integer where
+    prt = show
+
+instance Print a => Print (Maybe a) where
+    prt (Just a) = prt a
+    prt Nothing  = "Nothing"