Hi Malcolm
On Monday 05 March 2012 Malcolm Lear wrote:
It was I who required a way to do this. Thanks for this. Very well timed since
I now need to print unsigned 32 bit integers and unfortunately none of the DEC$
functions can do this. Hopefully a few changes to this will provide a solution.
This was the comma$ function I wrote ...
750 DEFine FuNction comma$(num)
760 LOCal t, fra
770 IF num < 0 : RETurn "-" & comma$(ABS(num))
780 IF num < 1000 : RETurn num
790 IF num/1000 > 2^31-2 : RETurn num : REMark otherwise INT(num/1000) will
fail
800 t = INT(num/1000)
810 fra = num - t*1000 : IF "e-" INSTR fra : fra = 0
820 RETurn comma$((t)) & "," & FILL$("0",(fra<100)+(fra<10)+(fra<1 AND fra>0))
& fra
830 END DEFine comma$
This function seems to be accurate for all integers within the 32 bit range.
With higher values precision would be lost.
If I understand correctly, you want to print integers from 0 up to 2^32-1, when
they are stored in the form -2^31 up to 2^31-1. For a negative number, the
absolute value is subtracted from 2^32.
Because we are outside of the 32 bit range of precision, subtraction is done
using strings, with each digit subtracted separately, working from the right
hand end to the left, using a carry flag, similar to the method used in primary
school arithmetic. This suggests something like the following ...
28430 DEFine FuNction unsigned_32bit$(num)
28440 LOCal x$(14), top$(13), bot$(13), ans$(13), carry, i, sum
28450 IF num < -2^31 OR num >= 2^31 : RETurn num
28460 IF ABS(num) - INT(ABS(num)) <> 0 : RETurn num
28470 x$ = comma$(num) : IF x$(1) <> "-" : RETurn x$
28480 top$ = comma$(2^32)
28490 bot$ = "0,000,000,000" : ans$ = bot$
28500 bot$(15-LEN(x$) TO 13) = x$(2 TO LEN(x$))
28510 carry = 0
28520 FOR i = 13,12,11, 9,8,7, 5,4,3, 1
28530 sum = top$(i) - ( bot$(i) + carry )
28540 IF sum < 0 : carry = 1 : ELSE carry = 0
28550 ans$(i) = sum + carry * 10
28560 END FOR i
28570 RETurn ans$
28580 END DEFine unsigned_32bit$
PRINT unsigned_32bit$(-1) gives 4,294,967,295
Michael Bulford
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