public int Evaluate()
{
if (!IsConstant())
{
throw new InvalidOperationException();
}
switch (Op)
{
case ArithSpec.Add:
return(S1.Evaluate() + S2.Evaluate());
case ArithSpec.Subtract:
return(S1.Evaluate() - S2.Evaluate());
case ArithSpec.Multiply:
return(S1.Evaluate() * S2.Evaluate());
case ArithSpec.Divide:
return(S1.Evaluate() / S2.Evaluate());
default:
throw new InvalidOperationException();
}
}