[project @ 2003-07-09 11:08:03 by simonpj]

[ghc-hetmet.git] / ghc / compiler / basicTypes / BasicTypes.lhs

diff --git a/ghc/compiler/basicTypes/BasicTypes.lhs b/ghc/compiler/basicTypes/BasicTypes.lhs
index 42e5e9f..1f74e7f 100644 (file)
--- a/ghc/compiler/basicTypes/BasicTypes.lhs
+++ b/ghc/compiler/basicTypes/BasicTypes.lhs
@@ -20,8 +20,10 @@ module BasicTypes(
 
        Unused, unused,
 
-       Fixity(..), FixityDirection(..),
-       defaultFixity, maxPrecedence, negateFixity, negatePrecedence,
+       FixitySig(..), Fixity(..), FixityDirection(..),
+       defaultFixity, maxPrecedence, 
+       arrowFixity, negateFixity, negatePrecedence,
+       compareFixity,
 
        IPName(..), ipNameName, mapIPName,
 
@@ -44,12 +46,15 @@ module BasicTypes(
        StrictnessMark(..), isMarkedUnboxed, isMarkedStrict,
 
        CompilerPhase, 
-       Activation(..), isActive, isNeverActive, isAlwaysActive
+       Activation(..), isActive, isNeverActive, isAlwaysActive,
+
+       SuccessFlag(..), succeeded, failed, successIf
    ) where
 
 #include "HsVersions.h"
 
 import Outputable
+import SrcLoc
 \end{code}
 
 %************************************************************************
@@ -135,31 +140,73 @@ mapIPName f (Linear  n) = Linear  (f n)
 %************************************************************************
 
 \begin{code}
+------------------------
+data FixitySig name = FixitySig name Fixity SrcLoc 
+
+instance Eq name => Eq (FixitySig name) where
+   (FixitySig n1 f1 _) == (FixitySig n2 f2 _) = n1==n2 && f1==f2
+
+instance Outputable name => Outputable (FixitySig name) where
+  ppr (FixitySig name fixity loc) = sep [ppr fixity, ppr name]
+
+------------------------
 data Fixity = Fixity Int FixityDirection
-data FixityDirection = InfixL | InfixR | InfixN 
-                    deriving(Eq)
 
 instance Outputable Fixity where
     ppr (Fixity prec dir) = hcat [ppr dir, space, int prec]
 
+instance Eq Fixity where               -- Used to determine if two fixities conflict
+  (Fixity p1 dir1) == (Fixity p2 dir2) = p1==p2 && dir1 == dir2
+
+------------------------
+data FixityDirection = InfixL | InfixR | InfixN 
+                    deriving(Eq)
+
 instance Outputable FixityDirection where
     ppr InfixL = ptext SLIT("infixl")
     ppr InfixR = ptext SLIT("infixr")
     ppr InfixN = ptext SLIT("infix")
 
-instance Eq Fixity where               -- Used to determine if two fixities conflict
-  (Fixity p1 dir1) == (Fixity p2 dir2) = p1==p2 && dir1 == dir2
-
+------------------------
 maxPrecedence = (9::Int)
 defaultFixity = Fixity maxPrecedence InfixL
 
 negateFixity :: Fixity
 negateFixity     = Fixity negatePrecedence InfixL      -- Precedence of unary negate is wired in as infixl 6!
 
+arrowFixity :: Fixity  -- Fixity of '->' in types
+arrowFixity = Fixity 0 InfixR
+
 negatePrecedence :: Int
 negatePrecedence = 6
 \end{code}
 
+Consider
+
+\begin{verbatim}
+       a `op1` b `op2` c
+\end{verbatim}
+@(compareFixity op1 op2)@ tells which way to arrange appication, or
+whether there's an error.
+
+\begin{code}
+compareFixity :: Fixity -> Fixity
+             -> (Bool,         -- Error please
+                 Bool)         -- Associate to the right: a op1 (b op2 c)
+compareFixity (Fixity prec1 dir1) (Fixity prec2 dir2)
+  = case prec1 `compare` prec2 of
+       GT -> left
+       LT -> right
+       EQ -> case (dir1, dir2) of
+                       (InfixR, InfixR) -> right
+                       (InfixL, InfixL) -> left
+                       _                -> error_please
+  where
+    right       = (False, True)
+    left         = (False, False)
+    error_please = (True,  False)
+\end{code}
+
 
 %************************************************************************
 %*                                                                     *
@@ -376,6 +423,28 @@ instance Outputable StrictnessMark where
 
 %************************************************************************
 %*                                                                     *
+\subsection{Success flag}
+%*                                                                     *
+%************************************************************************
+
+\begin{code}
+data SuccessFlag = Succeeded | Failed
+
+successIf :: Bool -> SuccessFlag
+successIf True  = Succeeded
+successIf False = Failed
+
+succeeded, failed :: SuccessFlag -> Bool
+succeeded Succeeded = True
+succeeded Failed    = False
+
+failed Succeeded = False
+failed Failed    = True
+\end{code}
+
+
+%************************************************************************
+%*                                                                     *
 \subsection{Activation}
 %*                                                                     *
 %************************************************************************
@@ -412,3 +481,4 @@ isNeverActive act     = False
 isAlwaysActive AlwaysActive = True
 isAlwaysActive other       = False
 \end{code}
+