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Topic: Numeric Field Length RAF (Read 682 times) |
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joker
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Re: Numeric Field Length RAF
« Reply #2 on: Oct 23rd, 2015, 12:09am » |
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I'm away from my programming desk, but that makes sense. I just couldn't find anything like that in the literature available to me.
I'm converting everything to strings anyway, but I did have a number that needs a certain number of significant digits. I'll have to work that out.
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Richard Russell
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Re: Numeric Field Length RAF
« Reply #3 on: Oct 23rd, 2015, 09:01am » |
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on Oct 23rd, 2015, 12:09am, pnlawrence wrote:| I'm converting everything to strings anyway, but I did have a number that needs a certain number of significant digits. I'll have to work that out. |
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USING() will format a number to a given number of decimal places but LB 4 has no built-in mechanism for controlling the number of significant figures, which is a limitation. Fortunately LBB's USING() is extended and you can do it, but only by converting the number to scientific notation:
Code: pi = 4 * atn(1)
for i = 1 to 4
print using("#.####^^^^", pi)
pi *= 10
next i
Output from Code:3.1416E0
3.1416E1
3.1416E2
3.1416E3
More comprehensive control over numeric formatting can be achieved using Windows API calls, or by accessing BBC BASIC code from LBB, but they are 'advanced' techniques!
Note that LBB's floating-point ('real') variables have a precision of about 19 decimal digits compared with about 16 digits for LB 4.04 and 4.5.0. But when converted to a string, using STR$(), both LB and LBB preserve only 9 digits, so using numeric variables in a FIELD statement potentially results is a very significant loss of precision.
Richard.
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joker
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Re: Numeric Field Length RAF
« Reply #4 on: Oct 23rd, 2015, 10:16am » |
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Of course, RAFs are not intended to be database files with all of their intended complications, but for a little bit I was encouraged with LBs "numeric" FIELD design.
Curses! Dashed again! 
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Richard Russell
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Re: Numeric Field Length RAF
« Reply #5 on: Oct 23rd, 2015, 11:01am » |
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on Oct 23rd, 2015, 10:16am, pnlawrence wrote:| for a little bit I was encouraged with LBs "numeric" FIELD design. |
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A couple of points:
You can always do the numeric to string conversion yourself and then write the string to the RAF, that way you have complete control over precision etc.
Since LB/LBB can read and write any kind of file you can exactly reproduce the functionality of GET and PUT, or devise your own custom database format, using regular file-handling statements and functions such as PRINT# and INPUT$ in conjunction with SEEK. Richard.
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