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Transfering PTR to procs
Post by Matt on Jul 7th, 2013, 06:30am

Hi,

One of my programs requires records to be located using an index containing the pointers to each record. The routine opens the file and passes the file handle to a subroutine that loads the record. Due to the nature of the main routine, the file has to be opened first and then passed to the subroutine. However, I also have to pass the PTR to the subroutine via reference as well, as the subr assumes beginning of file otherwise.

This:
Code:
...
F% = OPENIN(file$)
PTR#F% = [indexed file ptr]
PROC_READ_RECORD(F%)
...

DEF PROC_READ_RECORD(fn%)
INPUT#fn%, text$
...

will not work.

I need to do this:
Code:
...
F% = OPENIN(file$)
PROC_READ_RECORD(F%, [indexed file ptr])
...

DEF PROC_READ_RECORD(fn%, ptr%)
PTR#fn% = ptr%
INPUT#fn%, text$
...


There is no real problem with doing this; it's just adding another parameter. I was just curious. Is this by design or the fact that a LOCAL variable is being used as the new file handle?

Matt
Re: Transfering PTR to procs
Post by admin on Jul 7th, 2013, 06:49am

on Jul 7th, 2013, 06:30am, Matt wrote:
There is no real problem with doing this; it's just adding another parameter.

There must be something wrong elsewhere in your program, since your first example - that you claim does not work - in fact is perfectly fine. A file is a global object, and if you set the file pointer in one part of your program it will remain set when accessed somewhere else. There's no way that simply calling a PROC can change it!

Go back to your original code, if you prefer it for simplicity, and debug the fault your end.

Richard.
Re: Transfering PTR to procs
Post by Matt on Jul 7th, 2013, 5:06pm

on Jul 7th, 2013, 06:49am, Richard Russell wrote:
There must be something wrong elsewhere in your program, since your first example - that you claim does not work - in fact is perfectly fine. A file is a global object, and if you set the file pointer in one part of your program it will remain set when accessed somewhere else. There's no way that simply calling a PROC can change it!

Go back to your original code, if you prefer it for simplicity, and debug the fault your end.



Mmm! Ok. Not sure what went wrong to start with. Just changed it and it worked fine. I did experiment with it at the start and it didn't seem to work what ever I did. Oh, well. Thanks.

Matt