Using PCSCJCTerminal to find the readers

Question

Hi,
there is a very strange thing that has happenned.
I am trying to develop an off-card application, that uses the jpcsc.dll (not the jct.dll)
to make it application portable accross the platforms. Thus, i have to use PCSCJCTerminal class, that works using jpcsc.dll and jpcsc.jar. Th eproblem is, that when i am trying to get all the readers attached to the machine, i can't:
listReaders() method seems to always return 0, despite the real number of readers attached.
This method works fine in e.g. NativeJCTerminal, bit then jct.dll is needed - i want to avoid using of it.
Could you tell me, where the error may have happened?
Code looks like this:
JCTerminal t = new PCSCJCTerminal();
t.init(" any|ed");
t.open();
t.listReaders(); //there zero is returnedI would appreciate any comments.
Best regards,
Eve

Answer 1

Your problem statement seems a little odd. If the robot can only go "down" or "left", then every sequence of moves will get him to (1,1) and all the sequences will have exactly the same length.
Also, I think perhaps you don't quite understand recursion. Even though a function is recursive, if-then-else still works the same way - only one of the branches will be taken, not both.
So for instance with the second version of the code that you posted, the initial call CountPaths(6,3) will result in just one recursive call to CountPaths(5,2). This in turn will result in a call to CountPaths(4,1). At that point, the calls will start falling into the earlier branch of the code and you will get calls to CountPaths(3,1), CountPaths(2,1), CountPaths(1,1). So then you will have a stack of six calls, each (except the last) waiting for the recursive call it made to return. CountPaths(1,1) returns without making a recursive call, and each of the others returns immediately (in reverse order) without making any other recursive calls.
On the other hand, if you really want the code to explore all the possible paths, it should recurse to explore the paths that begin with a "down" move and recurse again to explore the paths that begin with a "left" move. Something more like
CountPaths(IkeStreet-1, IkeAvenue);
CountPaths(IkeStreet, IkeAvenue-1);However, if you do just that without adding some adding some additional intelligence, you will find that you get a bit more than you bargained for.
Edited by: EricDittert on Sep 11, 2009 6:19 PM