two new functions in the PGF API: mkAbs, unAbs

src/runtime/haskell/PGF.hs

@@ -43,6 +43,7 @@ module PGF(
            -- ** Expr
            Expr,
            showExpr, readExpr,
+           mkAbs,    unAbs,
            mkApp,    unApp,
            mkStr,    unStr,
            mkInt,    unInt,

src/runtime/haskell/PGF/Expr.hs

@@ -1,6 +1,7 @@
 module PGF.Expr(Tree, BindType(..), Expr(..), Literal(..), Patt(..), Equation(..),
                 readExpr, showExpr, pExpr, pBinds, ppExpr, ppPatt, pattScope,
 
+                mkAbs,    unAbs,
                 mkApp,    unApp,
                 mkStr,    unStr,
                 mkInt,    unInt,
@@ -96,6 +97,15 @@ showExpr vars = PP.render . ppExpr 0 vars
 instance Read Expr where
     readsPrec _ = RP.readP_to_S pExpr
 
+mkAbs :: BindType -> CId -> Expr -> Expr
+mkAbs = EAbs
+
+unAbs :: Expr -> Maybe (BindType, CId, Expr)
+unAbs (EAbs bt x e) = Just (bt,x,e)
+unAbs (ETyped e ty) = unAbs e
+unAbs (EImplArg e)  = unAbs e
+unAbs _             = Nothing
+
 -- | Constructs an expression by applying a function to a list of expressions
 mkApp :: CId -> [Expr] -> Expr
 mkApp f es = foldl EApp (EFun f) es