Restart at beginning

[Robert E. Carneal]

I have a data file containing thousands of first names. I
randomly generate a number between 1 and 17547. Let's say
the number is 500. Then I will read the file and count the names
until the 500th name comes up.

If the user does not like it and wants a different name, is
there a command that will tell the program to start reading
the file from the beginning again? Like RESTORE for data lines?

I can work with CLOSE and just OPEN the file again, but is there
another way to start reading from the beginning again I wonder?

Thank you.

Robert Carneal

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[Mel Bishop]

Well, I can think of a couple of things. Both require opening
the file in binary mode

If the records in the data base are of fixed length, say 15
characters per record, generate the random number and multiply
that by 15 then subtract 15. i.e. n = int((n * 17547) * 15) - 15
and SEEK #1,N. One times 15 = 15 which would preclude selecting
the 1st entry in the data base. You would have to take Cr/Lf
into consideration if they are there.

Or you just could use the SEEK command to go to the 1st record
in the file. i.e. SEEK #1,0

I'm sure there are other methods of achieving your goal but this
gives you a couple of options to consider.

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[This message has been edited by Mel Bishop (edited August 10, 2002).]

[Bradley Callis]

Load them into an array. X =(Random Number) then name = namearray(x).
Of



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Thanks,

Bradley Callis

[Michael Mattias]

You don't need BINARY access... a RANDOM access file would be vastly easier to use and understand...

Simply store the first name list in a fixed record-length file...

TYPE RecordType
  FirstName  AS STRING * 20
END TYPE

DIM Record AS RecordType
OPEN "Firstnam.dat" FOR RANDOM AS #1 LEN = SIZEOF(Record)
FOR n=1 to NumNames
  LSET Record.firstname = (whatever) 
  PUT #1,N, Record
NEXT
CLOSE #1

.. and to retrieve a random record, get it by record number:

RandomNo = (however you get the random number)
GET #1, randomNo, Record
 INPUT " How about this one:" & Record.firstname & "?"; X$
 IF X$ = "Y" THEN
   ' yup, do this one
 ELSE
    whatever
 ....

MCM

[Alan Earnshaw]

The SEEK statement works with files opened in sequential mode. Just use

SEEK #x,0

where x is the file handle, and the second parameter is the offset from the beginning of the file. By using 0, you'll go back to the beginning of the file.

That said, I agree with Michael and Mel that random access or binary mode file access would be better choices.

Alan

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Alan C. Earnshaw
Information Management Systems, Inc.
http://www.infoms.com

[Michael Mattias]

Long time no see, Alan.

That said, the problem with SEEK is, "SEEK where?"

The only reason to use sequential access is that you have variable-length records terminated by CRLF. With variable-length records, record one obviously starts at offset (SEEK point) zero; but subsequent records may start anywhere and there is no way to 'calculate' the correct SEEK point. About all you could do to make SEEK useful with sequential access is read the whole file and save the SEEK point for each record in an array of INTEGERs or LONGs; then you could SEEK #hFile, SeekPoint%(n) to position the file pointer for a LINE INPUT which would get you record 'n'.

Of course, that might be a perfectly acceptable solution for this application if the firstname file does not change during program execution.

MCM

[Alan Earnshaw]

Ahh, but the original question was "...is there another way to start reading from the beginning...". There is, and that is SEEK #handle,0. As you noted, there are better ways to organize and read data files. But SEEK does what Robert wants to do.

Alan

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Alan C. Earnshaw
Information Management Systems, Inc.
http://www.infoms.com

[Michael Mattias]

..the original question was "...is there another way to start reading from the beginning...".

So you answered the <U>actual</U> user question? I guess that's why you are in software support and I'm not.

That, or I just knew instinctively that "going back to the begining so I can read everything sequentially again" was a non-optimal solution and subconsiously chose to ignore it.

MCM