[project @ 1996-04-07 15:41:24 by partain]

[ghc-hetmet.git] / ghc / compiler / hsSyn / HsExpr.lhs

diff --git a/ghc/compiler/hsSyn/HsExpr.lhs b/ghc/compiler/hsSyn/HsExpr.lhs
index fc9356a..8c62d18 100644 (file)
--- a/ghc/compiler/hsSyn/HsExpr.lhs
+++ b/ghc/compiler/hsSyn/HsExpr.lhs
@@ -45,17 +45,20 @@ data HsExpr tyvar uvar id pat
   | HsApp      (HsExpr tyvar uvar id pat)      -- application
                (HsExpr tyvar uvar id pat)
 
-  -- Operator applications and sections.
+  -- Operator applications:
   -- NB Bracketed ops such as (+) come out as Vars.
 
+  -- NB We need an expr for the operator in an OpApp/Section since
+  -- the typechecker may need to apply the operator to a few types.
+
   | OpApp      (HsExpr tyvar uvar id pat)      -- left operand
                (HsExpr tyvar uvar id pat)      -- operator
                (HsExpr tyvar uvar id pat)      -- right operand
 
-  -- ADR Question? Why is the "op" in a section an expr when it will
-  -- have to be of the form (HsVar op) anyway?
-  -- WDP Answer: But when the typechecker gets ahold of it, it may
-  -- apply the var to a few types; it will then be an expression.
+  -- We preserve prefix negation and parenthesis for the precedence parser.
+
+  | NegApp     (HsExpr tyvar uvar id pat)      -- negated expr
+  | HsPar      (HsExpr tyvar uvar id pat)      -- parenthesised expr
 
   | SectionL   (HsExpr tyvar uvar id pat)      -- operand
                (HsExpr tyvar uvar id pat)      -- operator
@@ -198,6 +201,7 @@ pprExpr sty expr@(HsApp e1 e2)
     collect_args (HsApp fun arg) args = collect_args fun (arg:args)
     collect_args fun            args = (fun, args)
 
+
 pprExpr sty (OpApp e1 op e2)
   = case op of
       HsVar v -> pp_infixly v
@@ -212,6 +216,13 @@ pprExpr sty (OpApp e1 op e2)
     pp_infixly v
       = ppSep [pp_e1, ppCat [pprOp sty v, pp_e2]]
 
+pprExpr sty (NegApp e)
+  = ppBeside (ppChar '-') (ppParens (pprExpr sty e))
+
+pprExpr sty (HsPar e)
+  = ppParens (pprExpr sty e)
+
+
 pprExpr sty (SectionL expr op)
   = case op of
       HsVar v -> pp_infixly v