yacc grammar / expressions parsed wrong ?

Hi,

I have a problem in getting my yacc grammer (byacc/j) / parser to
handle arithmetic expressions correctly.
- For the string "((b*c)+a)" the parser produces the equivalent
expression (b*c)+a.
- But for the string "a+(b*c)" the produced expression is (b*c)+(b*c).

The parser code which creates the add-expression is
{ yyval.obj = Expression.add   ( (Expression) val_peek(2).obj,
(Expression) val_peek(0).obj ); }

In the second case ("a+(b*c)") both val_peek(2).obj,  val_peek(0).obj
refer to the same Expression instance.

Here are the relevant parts of my grammar:

(...)

%left CMP_EQ CMP_NEQ CMP_LT CMP_LEQ CMP_GT CMP_GEQ
%left '&' '|' '^'
%left '+' '-'
%left '*' '/' '%'
%right '~' '!' CAST_TO_INT CAST_TO_BOOLEAN

(...)

expression:
          ConstExpr
       |  StreamOp
       |  TypeCastExpr
       /* CompareExpr */
       |  expression CMP_EQ expression  { $$ = Expression.cmpEq
( (Expression) $1, (Expression) $3 ); }
       |  expression CMP_NEQ expression { $$ =
Expression.cmpNeq( (Expression) $1, (Expression) $3 ); }
       |  expression CMP_LT expression  { $$ = Expression.cmpLt
( (Expression) $1, (Expression) $3 ); }
       |  expression CMP_LEQ expression { $$ =
Expression.cmpLEq( (Expression) $1, (Expression) $3 ); }
       |  expression CMP_GT expression  { $$ = Expression.cmpGt
( (Expression) $1, (Expression) $3 ); }
       |  expression CMP_GEQ expression { $$ =
Expression.cmpGEq( (Expression) $1, (Expression) $3 ); }
       /* UnaryExpr */
       |  '~' expression        { $$ = Expression.inv( (Expression)
$2 ); }
       |  '!' expression        { $$ = Expression.inv( (Expression)
$2 ); }
       |  '-' expression        { $$ = Expression.neg( (Expression)
$2 ); }
       /* MultiplicativeExpr */
       |  expression '*' expression     { $$ = Expression.mul
( (Expression) $1, (Expression) $3 ); }
       |  expression '/' expression     { $$ = Expression.div
( (Expression) $1, (Expression) $3 ); }
       |  expression '%' expression     { $$ = Expression.mod
( (Expression) $1, (Expression) $3 ); }
       |  expression '^' expression     { $$ = Expression.xor
( (Expression) $1, (Expression) $3 ); }
       /* AdditiveExpr */
       |  expression '+' expression     { $$ = Expression.add
( (Expression) $1, (Expression) $3 ); }
       |  expression '-' expression     { $$ = Expression.minus
( (Expression) $1, (Expression) $3 ); }
       |  expression '&' expression     { $$ = Expression.and
( (Expression) $1, (Expression) $3 ); }
       |  expression '|' expression     { $$ = Expression.or
( (Expression) $1, (Expression) $3 ); }
	   /* brackets */
       |  '(' expression ')'            { $$ = $2; }
       ;

I hope someone can see what I am doing wrong here.

Thanks in advance

Christian
[The usual problem is that you're not allocating space properly for
the tree nodes you create.  And please spell it "grammar". -John]