[project @ 2004-02-25 21:20:04 by ralf]

[haskell-directory.git] / Data / Generics / Text.hs

diff --git a/Data/Generics/Text.hs b/Data/Generics/Text.hs
index ccef471..b6ce518 100644 (file)
--- a/Data/Generics/Text.hs
+++ b/Data/Generics/Text.hs
@@ -28,7 +28,6 @@ import Prelude
 #endif
 import Control.Monad
 import Data.Maybe
-import Data.Typeable
 import Data.Generics.Basics
 import Data.Generics.Aliases
 import Text.ParserCombinators.ReadP
@@ -68,22 +67,26 @@ gread = readP_to_S gread'
 
  where
 
+  -- Helper for recursive read
   gread' :: Data a => ReadP a
-  gread' = gdefault `extR` scase
-
+  gread' = allButString `extR` stringCase
 
    where
 
     -- A specific case for strings
-    scase :: ReadP String
-    scase = readS_to_P reads
+    stringCase :: ReadP String
+    stringCase = readS_to_P reads
 
+    -- Determine result type
+    myDataType = dataTypeOf (getArg allButString)
+     where
+      getArg :: ReadP a -> a
+      getArg = undefined
 
     -- The generic default for gread
-    -- gdefault :: Data a => ReadP a
-    gdefault =
+    allButString =
       do
-               -- Drop "  (  "
+               -- Drop "  (  "
          skipSpaces                    -- Discard leading space
          char '('                      -- Parse '('
          skipSpaces                    -- Discard following space
@@ -100,29 +103,22 @@ gread = readP_to_S gread'
 
          return x
 
-     where
-
-       -- Get the datatype for the type at hand;
-       -- use gdefault to provide the type at hand.
-       myDataTypeOf :: Data a => ReadP a -> DataType
-       myDataTypeOf (_::ReadP a) = dataTypeOf (undefined::a)
-
-       -- Turn string into constructor driven by gdefault's type,
-       -- failing in the monad if it isn't a constructor of this data type
-       str2con :: String -> ReadP Constr       
-       str2con = maybe mzero return
-                . stringCon (myDataTypeOf gdefault)
+    -- Turn string into constructor driven by the requested result type,
+    -- failing in the monad if it isn't a constructor of this data type
+    str2con :: String -> ReadP Constr  
+    str2con = maybe mzero return
+            . stringCon myDataType
 
-       -- Get a Constr's string at the front of an input string
-       parseConstr :: ReadP String
-       parseConstr =  
+    -- Get a Constr's string at the front of an input string
+    parseConstr :: ReadP String
+    parseConstr =  
                string "[]"     -- Compound lexeme "[]"
           <++  infixOp        -- Infix operator in parantheses
           <++  readS_to_P lex  -- Ordinary constructors and literals
 
-       -- Handle infix operators such as (:)
-       infixOp :: ReadP String
-        infixOp = do c1  <- char '('
-                     str <- munch1 (not . (==) ')')
-                    c2  <- char ')'
-                    return $ [c1] ++ str ++ [c2]
+    -- Handle infix operators such as (:)
+    infixOp :: ReadP String
+    infixOp = do c1  <- char '('
+                 str <- munch1 (not . (==) ')')
+                c2  <- char ')'
+                 return $ [c1] ++ str ++ [c2]