div

1 files changed, 22 insertions, 10 deletions

diff --git a/examples/tutorial/calculator/CalculatorC.gf b/examples/tutorial/calculator/CalculatorC.gf
index f78d4f38b..cfef0e717 100644
--- a/examples/tutorial/calculator/CalculatorC.gf
+++ b/examples/tutorial/calculator/CalculatorC.gf
@@ -1,6 +1,6 @@
 --# -path=.:prelude
 
-concrete CalculatorC of Calculator = open Prelude in {
+concrete CalculatorC of Calculator = open Predef,Prelude in {
 
   flags lexer=codevars ; unlexer=code ;
 
@@ -10,27 +10,39 @@ concrete CalculatorC of Calculator = open Prelude in {
 
   lin
     PEmpty = ss [] ;
-    PDecl exp prog = ss ("int" ++ prog.$0 ++ "=" ++ exp.s ++ ";" ++ prog.s) ;
-    PAss vr exp prog = ss (vr.s ++ "=" ++ exp.s ++ ";" ++ prog.s) ;
+    PDecl exp prog = ss ("int" ++ prog.$0 ++ "=" ++ top exp ++ ";" ++ prog.s) ;
+    PAss vr exp prog = ss (vr.s ++ "=" ++ top exp ++ ";" ++ prog.s) ;
 
     EPlus  = infixl 0 "+" ;
     EMinus = infixl 0 "-" ;
     ETimes = infixl 1 "*" ;
+    EDiv   = infixl 1 "/" ;
 
     EInt i = constant i.s ;
     EVar x = constant x.s ;
 
   oper
-    Prec : PType = Predef.Ints 2 ;
+    Prec : PType = Ints 2 ;
     TermPrec : Type = {s : Str ; p : Prec} ;
 
-    usePrec : TermPrec -> Prec -> Str = \x,p ->
-      case <<x.p,p> : Prec * Prec> of {
-        <1,1> | <1,0> | <0,0> => x.s ;
-        <1,_> | <0,_>         => "(" ++ x.s ++ ")" ;
-        _ => x.s
+    lessPrec : Prec -> Prec -> Bool = \p,q ->
+      case <<p,q> : Prec * Prec> of {
+        <1,1> | <1,0> | <0,0> => False ;
+        <1,_> | <0,_>         => True ;
+        _ => False
         } ;
 
+    usePrec : TermPrec -> Prec -> Str = \x,p ->
+      case lessPrec x.p p of {
+        True => paren x.s ;
+        False => noparen x.s
+      } ;
+
+    paren : Str -> Str = \s -> "(" ++ s ++ ")" ;
+    noparen : Str -> Str = \s -> variants {s ; "(" ++ s ++ ")"} ;
+
+    top : TermPrec -> Str = \t -> usePrec t 0 ;
+
     mkPrec : Prec -> Str -> TermPrec = \p,s -> 
       {s = s ; p = p} ;
 
@@ -41,7 +53,7 @@ concrete CalculatorC of Calculator = open Prelude in {
 
     nextPrec : Prec -> Prec = \p -> case <p : Prec> of {
       2 => 2 ; 
-      n => Predef.plus n 1
+      n => plus n 1
       } ;
 
 }