+ppr_expr (HsProc pat (HsCmdTop cmd _ _ _) _)
+ = hsep [ptext SLIT("proc"), ppr pat, ptext SLIT("->"), pprExpr cmd]
+
+ppr_expr (HsArrApp arrow arg _ HsFirstOrderApp True _)
+ = hsep [ppr_expr arrow, ptext SLIT("-<"), ppr_expr arg]
+ppr_expr (HsArrApp arrow arg _ HsFirstOrderApp False _)
+ = hsep [ppr_expr arg, ptext SLIT(">-"), ppr_expr arrow]
+ppr_expr (HsArrApp arrow arg _ HsHigherOrderApp True _)
+ = hsep [ppr_expr arrow, ptext SLIT("-<<"), ppr_expr arg]
+ppr_expr (HsArrApp arrow arg _ HsHigherOrderApp False _)
+ = hsep [ppr_expr arg, ptext SLIT(">>-"), ppr_expr arrow]
+
+ppr_expr (HsArrForm (HsVar v) (Just _) [arg1, arg2] _)
+ = sep [pprCmdArg arg1, hsep [pprInfix v, pprCmdArg arg2]]
+ppr_expr (HsArrForm op _ args _)
+ = hang (ptext SLIT("(|") <> ppr_expr op)
+ 4 (sep (map pprCmdArg args) <> ptext SLIT("|)"))
+
+pprCmdArg :: OutputableBndr id => HsCmdTop id -> SDoc
+pprCmdArg (HsCmdTop cmd@(HsArrForm _ Nothing [] _) _ _ _) = ppr_expr cmd
+pprCmdArg (HsCmdTop cmd _ _ _) = parens (ppr_expr cmd)
+
+-- Put a var in backquotes if it's not an operator already
+pprInfix :: Outputable name => name -> SDoc
+pprInfix v | isOperator ppr_v = ppr_v
+ | otherwise = char '`' <> ppr_v <> char '`'
+ where
+ ppr_v = ppr v
+