Re: [abc-users] Tracematches local variable tracking

Hi Pavel,

Thanks for the answer. I realise that tracematches are used mainly for
tracing executions, but I was just curious.

Pavel Avgustinov wrote:
> Hi Alan,
>
> Indeed I don't think doing exactly what you describe is possible. Essentially
> you are asking for side effects while matching symbols to the program
> trace -- whenever a matching event occurs, you would like to update the
> internal 'account balance' counter.
>
> Tracematches aim to make the matching process completely declarative, and so
> this is not possible.
>
> Note that if you were only interested in a fixed, finite number of events, you
> could sort of emulate this: You could define, for your pattern,
> symbols "wd", "dp1" and "dp2". Giving the tracematch three more int-typed
> formal parameters, you could make each symbol bind the amount with an args()
> pointcut to one of the variables, and then in the tracematch body add them
> all up in the appropriate way.
>
> Still, it is not possible to do this for arbitrary traces containing
> withdrawals and deposits, as you don't know how many intermediate variables
> you'll need. For such a side-effect dependent computation, you'd probably be
> better off defining standard AspectJ after advice on the withdraw() and
> deposit() methods, which can appropriately update (say) an intertype-declared
> field on Account containing the balance of the transactions.
>
> HTH,
> - P
>
> On Wednesday 20 February 2008 15:11:58 Alan Teoh wrote:
>
>> Hi again,
>>
>> I was wondering if I can just use a tracematch alone to track the value
>> of a local variable across throughout the trace itself To illustrate the
>> problem, I have the following code:
>>
>> class Account {
>> private int type; // Integer to determine account type
>>
>> public Account(int t) {
>> this.type = t;
>> }
>>
>> public void withdraw(double amount) {
>> System.out.println("Withdraw");
>> }
>>
>> public void deposit(double amount) {
>> System.out.println("Deposit");
>> }
>>
>> public static void main(String[] args) {
>> Account a1 = new Account(1);
>> Account a2 = new Account(1);
>>
>> a1.withdraw(5);
>> a1.deposit(2);
>> a2.withdraw(2);
>> a1.deposit(6); // Match to occur here
>> a1.deposit(1);
>> }
>> }
>>
>> public aspect AccountTM {
>> tracematch (Account a) {
>> sym wd after:
>> call (* Account.withdraw(..)) && target(a);
>> sym dp after:
>> call (* Account.deposit(..)) && target(a);
>>
>> wd dp[2]
>> {
>> System.out.println("1 withdraw and 2 deposit method calls
>> made by " + a);
>> }
>> }
>> }
>>
>> As we can see the tracematch matches 1 withdraw() and 2 deposit() method
>> calls on a given object. My question is am I able to use just one
>> tracematch to track the value of "amount"? i.e. given the following calls
>> a1.withdraw(5);
>> a1.deposit(2);
>> a2.withdraw(2);
>> a1.deposit(6);
>> a1.deposit(1);
>>
>> As the regular expression matches the executions made by a1, I would
>> like to be able to keep track of the amount that was withdrawn and
>> deposited. So for that example above, I would have -5 + 2 + 6 = 3 as the
>> total amount withdrawn and deposited throughout the execution of a1.
>>
>> I have ideas over how to solve this, but I was wondering if I could do
>> it all using tracematches only? I was more inclined towards thinking
>> that it is not possible given the grammar specified for tracematches.
>>
>> Thanks.
>>
>
>
>
>
Received on Wed Feb 20 2008 - 16:15:29 GMT