public override void DoInstruction(ExpressionMediator exm, InstructionLine func, ProcessState state)
 {
     IOperandTerm term = ((ExpressionArgument)func.Argument).Term;
     SingleTerm ret = null;
     if (term != null)
     {
         ret = term.GetValue(exm);
     }
     state.ReturnF(ret);
 }