Modernise pragmas and extensions, fix use of State

Plugin/Pl/Common.hs

@@ -1,5 +1,3 @@
-{-# OPTIONS -fvia-C #-}
-
 module Plugin.Pl.Common (
         Fixity(..), Expr(..), Pattern(..), Decl(..), TopLevel(..),
         bt, sizeExpr, mapTopLevel, mapTopLevel', getExpr,

Plugin/Pl/Optimize.hs

@@ -1,4 +1,4 @@
-{-# OPTIONS -fvia-C -O2 -optc-O3 #-}
+{-# LANGUAGE ImplicitParams #-}
 module Plugin.Pl.Optimize (
     optimize,
   ) where

Plugin/Pl/Parser.hs

@@ -1,4 +1,3 @@
-{-# OPTIONS -fvia-C -O2 -optc-O3 #-}
 --
 -- Todo, use Language.Haskell
 --

Plugin/Pl/PrettyPrinter.hs

@@ -1,4 +1,5 @@
-{-# OPTIONS -fvia-C -fno-warn-orphans #-}
+{-# LANGUAGE PatternGuards #-}
+{-# OPTIONS_GHC -fno-warn-orphans #-}
 module Plugin.Pl.PrettyPrinter (Expr) where
 
 -- Dummy export to make ghc -Wall happy

Plugin/Pl/Rules.hs

@@ -1,7 +1,6 @@
-{-# OPTIONS -fvia-C #-}
-{-# OPTIONS -fno-warn-name-shadowing #-}
--- 6.4 gives a name shadow warning I haven't tracked down.
-
+{-# LANGUAGE ExistentialQuantification #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 --
 -- | This marvellous module contributed by Thomas J\344ger
 --

Plugin/Pl/Transform.hs

@@ -1,4 +1,4 @@
-{-# OPTIONS -fvia-C -O2 -optc-O3 #-}
+{-# LANGUAGE FlexibleInstances #-}
 module Plugin.Pl.Transform (
     transform,
   ) where
@@ -74,7 +74,7 @@ alphaRename e = alpha e `evalState` M.empty where
 
   -- act like a reader monad
   inEnv :: State s a -> State s a
-  inEnv (State f) = State $ \s -> (fst $ f s, s)
+  inEnv f = gets $ evalState f
 
   alphaPat (PVar v) = do
     fm <- get

pointfree.cabal

@@ -24,6 +24,11 @@ Source-repository head
 Executable pointfree
   Main-is:       Main.hs
   GHC-options:   -Wall
+  Extensions:    ExistentialQuantification,
+                 FlexibleInstances,
+                 ImplicitParams,
+                 PatternGuards,
+                 ScopedTypeVariables
   Build-depends: base >= 3 && < 4.4,
                  array >= 0.3 && < 0.4,
                  containers >= 0.3 && < 0.5,