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Forum Index : Microcontroller and PC projects : Simple Subtraction error?

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Phil23
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Joined: 27/03/2016
Location: Australia
Posts: 1667

Posted: 11:58am 13 Jun 2016

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Hi All,

Can anyone tell me what's going wrong here?

All I want to do is compare 2 numbers.....

Seeing unexpected results at the console.

[Code]
print 5-7
-2
> print tmpout
13.6875
> print tmpinp
14.25
> print tmpout-tmpinp
0.5625
> print 13.6875-14.25
0.5625
>print 2.5-4.8
-2.3
> print 2.5555-4.85
-2.2945
> print 13.6875-14.25
0.5625
> print 13.687-14.25
0.563
> print 13.68-14.25
0.57
> print 13.6-14.25
0.65
> print 13-14.25
-1.25

[/code]

Tried all those values & have no idea what's going on.

Thanks

Phil

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6269

Posted: 12:17pm 13 Jun 2016

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It is a good idea to give the version of MMBasic and the device (micromite or micromite+ etc)

It looks like a bug but without the version, it is difficult to check.

Jim

VK7JH
MMedit

WhiteWizzard
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Joined: 05/04/2013
Location: United Kingdom
Posts: 2932

Posted: 01:00pm 13 Jun 2016

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Works ok on MMBasic v5.1 on 28pinner (version 5.1 from Geoff's site)

Phil23
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Joined: 27/03/2016
Location: Australia
Posts: 1667

Posted: 01:03pm 13 Jun 2016

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TassyJim said It is a good idea to give the version of MMBasic and the device (micromite or micromite+ etc)

It looks like a bug but without the version, it is difficult to check.

Jim

Thanks Jim,

Realised that when I posted, particularly considering it's using the Beta.
Took a while to get back to update my post.

This is on the Beta, 5.2B2. 28 Pin Chip.

I just added TmpOut-TmpInp to the test code I was working on, ran it, Ctrl-C when I saw the positive value then played at the basic prompt.

The code is mainly test fragments.

Phil

2016-06-13_230310_Spa_Controller_V1.zip Edited by Phil23 2016-06-14

isochronic
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Joined: 21/01/2012
Location: Australia
Posts: 689

Posted: 03:59pm 13 Jun 2016

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It looks like the subtraction is reverse order sometimes - maybe
division is doing the same thing ?

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10209

Posted: 09:26pm 13 Jun 2016

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Definitely a bug in 5.2. I've written to Geoff separately to alert him.

Good catch Phil

Phil23
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Joined: 27/03/2016
Location: Australia
Posts: 1667

Posted: 11:34pm 13 Jun 2016

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matherp said Definitely a bug in 5.2. I've written to Geoff separately to alert him.
Good catch Phil

Well, It's my first Beta Bug experience...

But that's what Beta's are about, new features, and the simplest of existing functions that work, can unexpectedly take a turn, no guarantees.

Just good that it's been accidently uncovered.

Cheers.

My Office PC's all run Win7 Pro, Beta Pack 1;
Opps, That's Service Pack 1..........

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3282

Posted: 10:45pm 14 Jun 2016

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Yes, it is a bug.

The bug was introduced in beta 2 and was actually in the routine that converted the number to ASCII characters for display. It only caused problems when the number to be displayed was negative and less than one (eg, -0.45). So your compare would be correct, it was just how the number was displayed.

It will be fixed in the final release of V5.2.

Thanks for finding and reporting it, very much appreciated.

Geoff

EDIT:

Phil23 said But that's what Beta's are about, new features, and the simplest of existing functions that work, can unexpectedly take a turn, no guarantees.

Yes, very much, and a HUGE thanks to everyone who has used and/or found a bug in this and previous betas. Even if you just loaded the firmware and did not hit a bug that alone is valuable. Thanks EVERYONE very much, this software would not be half as good without your input.Edited by Geoffg 2016-06-16

Geoff Graham - http://geoffg.net

Grogster

Admin Group

Joined: 31/12/2012
Location: New Zealand
Posts: 9589

Posted: 04:51am 15 Jun 2016

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Nice one, Phil!!!

Only 315 posts old, and you have already found a rather subtle bug
Well done.

Another one squished.

Smoke makes things work. When the smoke gets out, it stops!

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