Use Pretty for errors and expressions

1 files changed, 24 insertions, 0 deletions

diff --git a/utils/CC/Pretty.hs b/utils/CC/Pretty.hs
index 0a41abe..ccb886a 100644
--- a/utils/CC/Pretty.hs
+++ b/utils/CC/Pretty.hs
@@ -2,8 +2,32 @@ module CC.Pretty where
 
 
 class Pretty a where
+    {-# MINIMAL pretty | prettyPrec #-}
     pretty :: a -> String
+    pretty = prettyPrec (-1)
 
+    -- | Higher precedence binds tighter.
+    -- Parentheses are required if the printed element has lower precedence
+    -- than the Int argument.
+    prettyPrec :: Int -> a -> String
+    prettyPrec _ = pretty
 
 instance Pretty Int where
     pretty = show
+
+
+-- Useful if you want the Pretty instance to be equal to the Show instance.
+newtype PrettyShow a = PrettyShow a
+  deriving (Show)
+
+instance Show a => Pretty (PrettyShow a) where
+    pretty (PrettyShow x) = show x
+
+
+pprint :: Pretty a => a -> IO ()
+pprint = putStrLn . pretty
+
+precParens :: Int -> Int -> String -> String
+precParens environ self s
+    | self < environ = "(" ++ s ++ ")"
+    | otherwise = s