Yes, I understand. But not without complicating the calculation to keep
track of the number of times I have done multiplication in the current
result.
Formating with current scale does not work.
: (format (* 9.9 9.789 9.56789) 20)
-> "9272347445790000000000000000000000000000000.00000000000000000000"
So in the example below I would have to track the number of arguments to
the * function. Then multiple that number against the current Scl value.
In the below would give me 3 * 20 giving 60 to scale the format. Is that
the best way to handle it? What if I have a a few dozen calculations
with multiples of arguments. Then do I do
(format num 50000) ?
And then significantly truncate the result to get the Scl number of
significant digits I wanted to track?
(format (* 9.9 9.789 9.56789) 60)
-> "927.234744579000000000000000000000000000000000000000000000000000"
(round (* 9.9 9.789 9.56789))
-> "9,272,347,445,790,000,000,000,000,000,000,000,000,000,000.000"
The decimal is not in the correct place.
I didn't know if PicoLisp provided a solution without complicating every
function which uses multiplication and division.
Thanks for the reply.
Jimmie
On 07/12/2017 01:05 PM, Aatos Heikkinen wrote:
I´ve found ´format´ and ´round´ functions quite helpful, see
https://the-m6.net/blog/fixed-point-arithmetic-in-picolisp.html
On 12 Jul 2017 18:52, "Jimmie Houchin" <jlhouc...@gmail.com
<mailto:jlhouc...@gmail.com>> wrote:
Hello,
I am trying to understand something about PicoLisp and Fixpoint
numbers.
I am writing an app and would consider PicoLisp should I get my
head around Lisp. But I do not understand how to use numbers.
I use a lot of floating point numbers and lots of calculations.
From simple experiments it seems that the numbers and math appear
to be accurate and correct. However I have no understanding of how
to present a final result formatted correctly.
Example:
(setq *Scl 5) ;; or could be 10 ...
(* 0.00009 0.0009)
-> 81
>From another language: 0.0000000081
or:
(setq *Scl 20)
(* 9.9 9.789 9.56789)
-> 927234744579000000000000000000000000000000000000000000000000000
>From another language 20 decimal points printed after converting
to floating point:
927.23474457900010747835
The math looks fine as far as these simple examples go. But if I
do several to dozens of different calculations with floating point
numbers with unknown values until streamed to the app from some
source. How do I know where the decimal point really belongs in
order to format correctly for human use? Is it possible?
I personally do not have a problem with fixpoint for internal use,
as that is simply an implementation issue. However I do need to
convert back to the best floating point representation for display
or storage.
Any help in understanding would be greatly appreciated.
Thanks.
Jimmie
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