Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Mark Waddingham
Hi Mark, What you have illustrated is precisely why JB was experiencing this problem in the first place (and precisely why most languages do not try to do anything clever when asked to truncate floating-point numbers). Due to the need to approximate floating-point numbers with a finite precision,

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Mark Wieder
Mark- Sunday, October 9, 2005, 4:58:45 AM, you wrote: > The solution to the issue you have here is to always add a small > 'epsilon' value to your numbers before truncating. Sorry, Mark, but that won't do it. on mouseUp local tValue put 179.71578291 into tValue put trunc(tV

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Ken Ray
On 10/9/05 7:41 AM, "Mark Waddingham" <[EMAIL PROTECTED]> wrote: > Floating-point arithmetic (which Revolution uses) works entirely in base > 2. However, while all decimal integers have an accurate representation > in binary, not all decimal fractions do and this is where the > approximation error

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Cubist
sez [EMAIL PROTECTED]: >I'm still trying to figure out how something as simple as ((36-34.2)*100) >can be anything but 180, or how (as Alex put it) "the binary double >precision representation of 34.2 is inexact"... Perhaps a few details will help clear up this question. .1 binary = .5 decim

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Mark Waddingham
Hi JB, > get ((36-34.2)*100) > put it & cr & trunc(it) Revolution has a 'numberFormat' property that determines to how many decimal places are used when numbers are converted to a string. The difference you are observing here is that the first line is the string representation of 'it' to (II

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Mark Waddingham
> Computers are the servants of humans, not the other way around. Computers only do precisely what they are told and, unfortunately, it is not always possible to instruct them to do things in a single way that satisfies everyone 100% of the time. Indeed, in cases where you might have a dozen diff

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread jbv
Mark, Thanks for your explanations. I fully understand the reasons why trunc((36-34.2)*100) returns 179. Nevertheless, I still don't understand why the following : get ((36-34.2)*100) put it & cr & trunc(it) returns : 180 179 at least javascript is less confusing, since ((36-34.2)*100)

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Mark Waddingham
Indeed, I believe MS Excel and most financial applications use a Decimal or BCD representation for arithmetic (or use floating-point in such a way to ensure the results are equivalent). Floating-point arithmetic (which Revolution uses) works entirely in base 2. However, while all decimal integers

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Mark Waddingham
I strongly agree that 'trunc' should come with a warning in the documentation as to its nature. Indeed, the corresponding function in perl (int) is documented quite clearly: "You should not use this function for rounding: one because it truncates towards 0, and two because machine representations

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Mark Waddingham
Hi JB, The solution to the issue you have here is to always add a small 'epsilon' value to your numbers before truncating. What is manifesting itself here is the innate approximation methods used by floating-point arithmetic, combined with the fact the trunc function does not shield you from thes

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Alex Tweedly
Richard Gaskin wrote: Maybe not. We know, for example, that Excel already accounts for this in its own code, correcting for the critical failure of the microprocessor designers. Anyone have time to check if RB, VB, and others do too? Python doesn't - though since it's a strongly typed (tho

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Chipp Walters
Richard Gaskin wrote: I believe the difference between accepting "179" from a computer when we all know the answer is "180" and accidentally enabling a robot to violate Asimov's Three Laws is one of degrees, not absolutes. Probably explains why my Roomba doesn't 'get the corners' too well. H

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread jbv
other environment tested : javascript IE 5.01 Mac OS9 (36 - 34.2) * 100->179.7 Math.floor((36 - 34.2) * 100)->179 IE 6 Win XP (36 - 34.2) * 100->179.71 Math.floor((36 - 34.2) * 100)->179 Firefox 1.0 Win XP (36 - 34.2) *

Re: Strange math behaviour... could someone explain this ?

2005-10-09 Thread Dom
Richard Gaskin <[EMAIL PROTECTED]> wrote: > > Bring BCD , that's what I say :-) > > "BCD"? Binary Coded Decimal? In the ancient times ;-) there were TWO versions of Microsoft Basic, one of them was a BCD version for accounting! Not for saying that this problem is a long time one ;-)) --

Re: Strange math behaviour... could someone explain this ?

2005-10-08 Thread Ken Ray
On 10/8/05 9:47 PM, "Richard Gaskin" <[EMAIL PROTECTED]> wrote: >> You might get Rev to introduce a workaround (e.g. by changing the >> effective meaning of trunc() to be "round at some ;eve; of precision >> that will do what I *want*, and then truncate", as Mark suggested) - but >> I fear that on

Re: Strange math behaviour... could someone explain this ?

2005-10-08 Thread Richard Gaskin
Alex Tweedly wrote: Richard Gaskin wrote: Computers are the servants of humans, not the other way around. You wish !! I know you well enough to know you're just having fun there, but because this anomaly has been accepted as "normal" in microprocessor design I hope the readers here will i

Re: Strange math behaviour... could someone explain this ?

2005-10-08 Thread Alex Tweedly
Richard Gaskin wrote: One man's "artifact" is another man's "bug". :) The original poster never specified that it was a Rev bug, The *original* poster (jbv) didn't, but Jonathan (to whom I was replying) did. At least, he said that Rev did this, and he said (in an earlier email) that it wa

Re: Strange math behaviour... could someone explain this ?

2005-10-08 Thread Mark Wieder
Alex- Friday, October 7, 2005, 11:14:47 AM, you wrote: > It's NOT a Rev bug - it's an artifact of double precision binary > arithmetic (or, if you like, an artifact of the IEEE format used by > Intel (and everyone else)). I'm sure if I coded the same thing in java I would also come up with 179.

Re: Strange math behaviour... could someone explain this ?

2005-10-08 Thread Eric Chatonet
Hi all, set the numberformat to "0.0" put (36-34.2)*100 into temp put temp & cr & trunc(temp) & cr & trunc(180) Result: 180.0 179.0 180.0 Difficult to name this a man's bug ;-) Le 8 oct. 05 à 03:41, Richard Gaskin a écrit : Alex Tweedly wrote: Lynch, Jonathan wrote: But s

Re: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Richard Gaskin
Alex Tweedly wrote: Lynch, Jonathan wrote: But still... Answer trunc((36-34.2)*100) should return 180, not 179. No it shouldn't. I mean, the underlying code should work to return an accurate value. It does. Perhaps it is just a matter of opinion, but to me, if the software returns a wr

Re: Strange math behaviour... could someone explain this ?

2005-10-07 Thread curry
FWIW: In MS Excel (v.97, on Windows), "=TRUNC((36-34.2)*100)" gives 180. :-) Curry Kenworthy Curry K. Software http://curryk.com ___ use-revolution mailing list use-revolution@lists.runrev.com Please visit this url to subscribe, unsubscribe and man

Re: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Ken Ray
On 10/7/05 2:30 PM, "jbv" <[EMAIL PROTECTED]> wrote: > Nevertheless, how do you explain that the following : > > put 36 into A > put 34.2 into B > put A-B into C > > put C*100 into C > put trunc(C) > > returns 180 with Rev 2.5 on Mac OS9, but returns 179 on other > platforms such as L

Re: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Alex Tweedly
jbv wrote: Nevertheless, how do you explain that the following : put 36 into A put 34.2 into B put A-B into C put C*100 into C put trunc(C) returns 180 with Rev 2.5 on Mac OS9, but returns 179 on other platforms such as Linux or Win2000 ? Just curious... I was curious about that too

Re: Strange math behaviour... could someone explain this ?

2005-10-07 Thread jbv
Alex, > Users of trunc() (whichever language they use it in :-) should be wary > of the dangers. > Thank you so much for your explanations. As for rev users, I strongly suggest that this "potential problem" should be mentioned in the doc, at least in the part dedicated to the trunc() function..

RE: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Lynch, Jonathan
>It's NOT a Rev bug - it's an artifact of double precision binary arithmetic >(or, if you like, an artifact of the IEEE format used by Intel (and >everyone else)). Alex, your explanation makes perfect sense, and I accept that it is not a Rev bug. But... I still don't like it, though. This affe

Re: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Alex Tweedly
Lynch, Jonathan wrote: But still... Answer trunc((36-34.2)*100) should return 180, not 179. No it shouldn't. I mean, the underlying code should work to return an accurate value. It does. Perhaps it is just a matter of opinion, but to me, if the software returns a wrong value in a cal

RE: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Lynch, Jonathan
AM To: How to use Revolution Subject: Re: Strange math behaviour... could someone explain this ? Lynch, Jonathan wrote: >Even just this simple line produces the same error: > >Somehow, Rev is performing 36-34.2, and even though it displays that >number as 1.8, it must be processing i

RE: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Lynch, Jonathan
behaviour... could someone explain this ? Lynch, Jonathan wrote: >Even just this simple line produces the same error: > >Somehow, Rev is performing 36-34.2, and even though it displays that >number as 1.8, it must be processing it internally as >1.799 or some

RE: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Lynch, Jonathan
179 > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of jbv > Sent: Friday, October 07, 2005 10:02 AM > To: How to use Revolution > Subject: Re: Strange math behaviour... could someone explain this ? > > According to my tests (which aren

RE: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Lynch, Jonathan
get 179 > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of jbv > Sent: Friday, October 07, 2005 10:02 AM > To: How to use Revolution > Subject: Re: Strange math behaviour... could someone explain this ? > > According to my tests (which are

Re: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Alex Tweedly
Lynch, Jonathan wrote: Even just this simple line produces the same error: Somehow, Rev is performing 36-34.2, and even though it displays that number as 1.8, it must be processing it internally as 1.799 or something like that. Very disturbing - This could affect a prog

Re: Strange math behaviour... could someone explain this ?

2005-10-07 Thread jbv
-Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of jbv > Sent: Friday, October 07, 2005 10:02 AM > To: How to use Revolution > Subject: Re: Strange math behaviour... could someone explain this ? > > According to my tests (which aren't exha

RE: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Lynch, Jonathan
I just tried this script - but I still get 179 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of jbv Sent: Friday, October 07, 2005 10:02 AM To: How to use Revolution Subject: Re: Strange math behaviour... could someone explain this ? According to my tests

Re: Strange math behaviour... could someone explain this ?

2005-10-07 Thread jbv
According to my tests (which aren't exhaustive) there seems to be another workaround : put 36 into A put 34.2 into B put A-B into C put C*100 into C put trunc(C) this gives 180 as a result, while the following line (replacing the last 2 of the above example) gives 179 put trunc(C*10

RE: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Lynch, Jonathan
? -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Lynch, Jonathan Sent: Friday, October 07, 2005 9:32 AM To: How to use Revolution Subject: RE: Strange math behaviour... could someone explain this ? Even just this simple line produces the same error: answer

RE: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Lynch, Jonathan
k properly. That makes me wonder if any other math functions might have some underlying weirdness. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Lynch, Jonathan Sent: Friday, October 07, 2005 9:13 AM To: How to use Revolution Subject: RE: Strange math

RE: Strange math behaviour... could someone explain this ?

2005-10-07 Thread Lynch, Jonathan
I get the same thing... That's gotta be a bug. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of jbv Sent: Friday, October 07, 2005 7:17 AM To: How to use Revolution Subject: Strange math behaviour... could someone explain this ? Hi list, example 1 :