private Surface.Expr Expr()
{
Surface.Expr left = Term();
int type = lookahead.Type;
switch (type)
{
case SchoolLexer.ADD:
case SchoolLexer.SUB:
Consume();
break;
default:
return(left);
}
Surface.Expr right = Expr();
Surface.Expr expr;
switch (type)
{
case SchoolLexer.ADD:
expr = new Surface.Add(left, right);
break;
case SchoolLexer.SUB:
expr = new Surface.Sub(left, right);
break;
default:
throw new ParserException("unreachable code");
}
return(expr);
}
Core.Expr Surface.IExprVisitor <Core.Expr> .Visit(Surface.Sub sub)
{
Core.Expr left = sub.Left.Accept(this);
Core.Expr right = sub.Right.Accept(this);
return(new Core.FunApp("sub", new Core.Expr[] { left, right }));
}
object Surface.IExprVisitor <object> .Visit(Surface.Sub sub)
{
PrintBinaryOperator(sub, '-');
return(null);
}