private bool ExpectInt(Expression exp, Token t, bool isRightHandSide)
{
if (!(exp is TypedExpression<int>)) {
errors.SemErr(t.line, t.col, string.Format("'{0}' expects an integer expression on its {1} side", t.val, isRightHandSide ? "right" : "left"));
return false;
}
return true;
}