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Topic: Transfering PTR to procs (Read 684 times) |
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Matt
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Transfering PTR to procs
« Thread started on: Jul 7th, 2013, 06:30am » |
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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
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admin
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Posts: 1145
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Re: Transfering PTR to procs
« Reply #1 on: Jul 7th, 2013, 06:49am » |
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on Jul 7th, 2013, 06:30am, Matt wrote:| There is no real problem with doing this; it's just adding another parameter. |
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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.
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Matt
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Re: Transfering PTR to procs
« Reply #2 on: Jul 7th, 2013, 5:06pm » |
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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.
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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
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