[project @ 1997-09-03 23:51:26 by sof]

[ghc-hetmet.git] / ghc / compiler / utils / Maybes.lhs

diff --git a/ghc/compiler/utils/Maybes.lhs b/ghc/compiler/utils/Maybes.lhs
index 1465534..b29dd9c 100644 (file)
--- a/ghc/compiler/utils/Maybes.lhs
+++ b/ghc/compiler/utils/Maybes.lhs
@@ -4,16 +4,14 @@
 \section[Maybes]{The `Maybe' types and associated utility functions}
 
 \begin{code}
-#if defined(COMPILING_GHC)
 #include "HsVersions.h"
-#endif
 
 module Maybes (
 --     Maybe(..), -- no, it's in 1.3
        MaybeErr(..),
 
-       allMaybes,      -- GHCI only
-       catMaybes,
+       mapMaybe,
+       allMaybes,
        firstJust,
        expectJust,
        maybeToBool,
@@ -24,27 +22,19 @@ module Maybes (
        failMaB,
        failMaybe,
        seqMaybe,
-       mapMaybe,       -- GHCI only
        returnMaB,
-       returnMaybe,    -- GHCI only
+       returnMaybe,
        thenMaB,
-       thenMaybe       -- GHCI only
-
-#if ! defined(COMPILING_GHC)
-       , findJust
-       , foldlMaybeErrs
-       , listMaybeErrs
-#endif
+       catMaybes
     ) where
 
-#if defined(COMPILING_GHC)
+CHK_Ubiq()             -- debugging consistency check
+import Unique  (Unique)        -- only for specialising
 
-CHK_Ubiq() -- debugging consistency check
-
-#if USE_ATTACK_PRAGMAS
-import Util
-#endif
+#if __GLASGOW_HASKELL__ >= 204
+import Maybe( catMaybes, mapMaybe )
 #endif
+
 \end{code}
 
 
@@ -55,14 +45,6 @@ import Util
 %************************************************************************
 
 \begin{code}
-#if __HASKELL1__ < 3
-data Maybe a
-  = Nothing
-  | Just a
-#endif
-\end{code}
-
-\begin{code}
 maybeToBool :: Maybe a -> Bool
 maybeToBool Nothing  = False
 maybeToBool (Just x) = True
@@ -74,17 +56,26 @@ a list of @Justs@ into a single @Just@, returning @Nothing@ if there
 are any @Nothings@.
 
 \begin{code}
-catMaybes :: [Maybe a] -> [a]
-catMaybes []               = []
-catMaybes (Nothing : xs)   = catMaybes xs
-catMaybes (Just x : xs)           = (x : catMaybes xs)
-
 allMaybes :: [Maybe a] -> Maybe [a]
 allMaybes [] = Just []
 allMaybes (Nothing : ms) = Nothing
 allMaybes (Just x  : ms) = case (allMaybes ms) of
                             Nothing -> Nothing
                             Just xs -> Just (x:xs)
+
+#if __GLASGOW_HASKELL__ < 204
+       -- After 2.04 we get these from the library Maybe
+catMaybes :: [Maybe a] -> [a]
+catMaybes []               = []
+catMaybes (Nothing : xs)   = catMaybes xs
+catMaybes (Just x : xs)           = (x : catMaybes xs)
+
+mapMaybe :: (a -> Maybe b) -> [a] -> [b]
+mapMaybe f [] = []
+mapMaybe f (x:xs) = case f x of
+                       Just y  -> y : mapMaybe f xs
+                       Nothing -> mapMaybe f xs
+#endif
 \end{code}
 
 @firstJust@ takes a list of @Maybes@ and returns the
@@ -115,13 +106,6 @@ expectJust err Nothing  = error ("expectJust " ++ err)
 The Maybe monad
 ~~~~~~~~~~~~~~~
 \begin{code}
-#if __HASKELL1__ < 3
-thenMaybe :: Maybe a -> (a -> Maybe b) -> Maybe b
-m `thenMaybe` k = case m of
-                 Nothing -> Nothing
-                 Just a  -> k a
-#endif
-
 seqMaybe :: Maybe a -> Maybe a -> Maybe a
 seqMaybe (Just x) _  = Just x
 seqMaybe Nothing  my = my
@@ -131,12 +115,6 @@ returnMaybe = Just
 
 failMaybe :: Maybe a
 failMaybe = Nothing
-
-mapMaybe :: (a -> Maybe b) -> [a] -> Maybe [b]
-mapMaybe f []    = returnMaybe []
-mapMaybe f (x:xs) = f x                        `thenMaybe` \ x' ->
-                   mapMaybe f xs       `thenMaybe` \ xs' ->
-                   returnMaybe (x':xs')
 \end{code}
 
 Lookup functions
@@ -154,17 +132,11 @@ assocMaybe alist key
     lookup []            = Nothing
     lookup ((tv,ty):rest) = if key == tv then Just ty else lookup rest
 
-#if defined(COMPILING_GHC)
-{-? SPECIALIZE assocMaybe
-       :: [(String,        b)] -> String        -> Maybe b,
-          [(Id,            b)] -> Id            -> Maybe b,
-          [(Class,         b)] -> Class         -> Maybe b,
-          [(Int,           b)] -> Int           -> Maybe b,
-          [(Name,          b)] -> Name          -> Maybe b,
-          [(TyVar,         b)] -> TyVar         -> Maybe b,
-          [(TyVarTemplate, b)] -> TyVarTemplate -> Maybe b
+{-# SPECIALIZE assocMaybe
+       :: [(FAST_STRING,   b)] -> FAST_STRING -> Maybe b
+        , [(Int,           b)] -> Int         -> Maybe b
+        , [(Unique,        b)] -> Unique      -> Maybe b
   #-}
-#endif
 \end{code}
 
 @mkLookupFun eq alist@ is a function which looks up
@@ -218,38 +190,3 @@ returnMaB v = Succeeded v
 failMaB :: err -> MaybeErr val err
 failMaB e = Failed e
 \end{code}
-
-
-@listMaybeErrs@ takes a list of @MaybeErrs@ and, if they all succeed, returns
-a @Succeeded@ of a list of their values.  If any fail, it returns a
-@Failed@ of the list of all the errors in the list.
-
-\begin{code}
-listMaybeErrs :: [MaybeErr val err] -> MaybeErr [val] [err]
-listMaybeErrs
-  = foldr combine (Succeeded [])
-  where
-    combine (Succeeded v) (Succeeded vs) = Succeeded (v:vs)
-    combine (Failed err)  (Succeeded _)         = Failed [err]
-    combine (Succeeded v) (Failed errs)         = Failed errs
-    combine (Failed err)  (Failed errs)         = Failed (err:errs)
-\end{code}
-
-@foldlMaybeErrs@ works along a list, carrying an accumulator; it
-applies the given function to the accumulator and the next list item,
-accumulating any errors that occur.
-
-\begin{code}
-foldlMaybeErrs :: (acc -> input -> MaybeErr acc err)
-              -> acc
-              -> [input]
-              -> MaybeErr acc [err]
-
-foldlMaybeErrs k accum ins = do_it [] accum ins
-  where
-    do_it []   acc []    = Succeeded acc
-    do_it errs acc []    = Failed errs
-    do_it errs acc (v:vs) = case (k acc v) of
-                             Succeeded acc' -> do_it errs       acc' vs
-                             Failed err     -> do_it (err:errs) acc  vs
-\end{code}