Re: bcd
a.tammer at hetnet.nl wrote:
>before i really start putting things together, i'd like to establish limits
>on an actual [real world] precision to be achieved by the routines,
20 before the decimal point plus 10 after is IMO well over the top.
I used 15,7 for 12 years & I twice needed 16 before and once 8 after.
I'd prefer a variable-length variety, with most values fitting in 8
bytes. There is also an argument for letting the programmer "fix" the
precision so a) you don't actually need to store an exponent against
each number, and b) comparison (esp during a sort) is nice & fast.
> as well
>as the maximum number of digits to be displayable. more or less like setting
>a standard for EFP-calculations.
A Romanian Oil company wanted 16,3. Nothing I've ever done wanted more
than 6dp printed. More common was the case that it had to be printed
in say 10 characters, so after [+/-]9,999.99[space], print 100.00K,
thru [+/-]9,999.99K then M, etc.
>'tho i could do 9 digits in an integer on 2nd thought i choose to do 8 as
>this would give a real time-gain on mult() and pow() that will far outweigh
>the storage-penalty of 12.5/100.
I was thinking along those lines myself after your last post.
>
>having said my main piece, i'd like to be quite open with you all. i'm more
>of a conceptualist than i'm an EU-progger or even progger per se. most of
>you lady(ies) and gents with far more experience than me in EU will be able
>to do the actual coding a lot faster than i can. i nevertheless will do it
>of course, 'tho i like the idea of a small team with a math-head, a fluent
>progger/coder working with me on my concept, which i will put in a small
>paper (app. 3*A4) today and post to those willing to join the team by this
>time to-morrow.
Consider me interested.
On Sun, 14 Apr 2002 18:41:36 -0300, rforno at tutopia.com wrote:
>There is a thing I still do not understand: what are the advantages of doing
>BCD math instead of using standard binary math with, let's say, cents
>instead of dollars, and then converting to dollars and cents only at the
>output? This is for commercial applications.
I struggle to see any real advantages without adding to
atom/object/sequence, or "with bcd" replacing float.
I still want one day to see "if 0.1+0.2=0.3 then" useable, as is,
whether that means I must suffer a performance hit, or not..
>Of course this does not consider huge or very small quantities with many,
>many digits precision, but they still could be managed with the approach I
>suggest using binary rather than decimal arithmetic, which would be faster.
You still have that choice.
Maybe this is just an experiment which may work, may not.
Pete
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