On 8 Feb 2009, at 04:30, Jim Starkey wrote:
Konstantin Osipov wrote:
* Jim Starkey <[email protected]> [09/01/16 08:01]:
A more intelligent, denser, faster, and more intuitive format
would use a single vector of binary words. On a challenge from
Monty (W.), I did a relative performance measure between the
Falcon decimal type and the "server" type. The worst case (> 18
decimal digits of precision) showed Falcon 40% faster. For
anything less than 18 decimal digits of precision, Falcon was
approximately infinitely faster (Falcon uses a 64 bit int with a
decimal scale factor).
There is no precise conversion from base 2/4/8/16 representation to
base
5/10 representation when you have digits after the (decimal,
binary) point.
That's why base 2 representation just can't be used.
You better give an example. Good luck. I think you will find that
123.45 can be represented as 12,345 with a decimal scale of 2.
I'd have to agree with Jim here. I think you're confusing how floating
point is traditionally represented and looking at the problem as
simply " x * 10^(-y) ". The problems of storing and manipulating large
integers has already been solved, only need to implement the other bit.
That was why I was surprised that an existing 'big integer' library
wasn't used when my_decimal first hit the tree. I wasn't able to argue
for the removal of my_decimal (other than the fact that I didn't like
it) because I didn't have the data on hand and *anything* would have
been better than the decimal implementation which was there before it.
As a semi-random side note... A 32bit Pascal compiler I used from the
1990's had a "Currency" type which was represented by a 63 bit signed
number which had a fixed decimal precision 10^-4. Fast, simple,
accurate, effective and completely transparent to the programmer. I
liked it and since then, I have implemented similar things whenever I
manipulate currency for my own projects.
Regards,
Antony.
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