7 / 8.0 roundTo 0.01 = 0.88 Aha! Thanks!

But:

100 * (1.05 raisedTo: 10) roundTo: 0.01 162.89000000000001

"162.88946267774418" "unrounded" 100 * (1.05 raisedTo: 15) roundTo: 0.01 207.89000000000001

"207.8928179411367" "unrounded" Bug, or me again :-)

MacBook Pro (Retina, 15-inch, Early 2013) System Version: OS X 10.10.2 (14C109)

Image ----- /Users/chuck/Downloads/Squeak-4.5-All-In-One/Squeak-4.5-All-in-One.app/Contents/Resources/Squeak4.5-13680.image Squeak4.5 latest update: #13680 Current Change Set: Unnamed1 Image format 6505 (32 bit)

Virtual Machine --------------- /Users/chuck/Downloads/Squeak-4.5-All-In-One/Squeak-4.5-All-in-One.app/Contents/MacOS/Squeak Croquet Closure Cog VM [CoInterpreter VMMaker.oscog-eem.331] 4.5 Mac OS X built on Aug 22 2013 10:08:05 Compiler: 4.2.1 (Apple Inc. build 5666) (dot 3) platform sources revision VM: r2776 http://www.squeakvm.org/svn/squeak/branches/Cog Plugins: r2545 http://squeakvm.org/svn/squeak/trunk/platforms/Cross/plugins CoInterpreter VMMaker.oscog-eem.331 uuid: 37d2e4b0-2f37-4e2d-8313-c63637785e59 Aug 22 2013 StackToRegisterMappingCogit VMMaker.oscog-eem.333 uuid: 84da9cb8-7f30-4cb7-b4fb-239a11f63b54 Aug 22 2013

On Wed, Feb 4, 2015 at 2:59 AM, Ben Coman btc@openinworld.com wrote:

In the interest of teaching how to fish, look at the senders of #roundTo: to find its usage.

I'll post a full answer tomorrow if you don't beat me to it.

cheers -ben

On Wed, Feb 4, 2015 at 4:34 PM, Chuck Hipschman ckhipschman@gmail.com wrote:

...

7 / 8.0 roundTo: 2 I expect 0.88, I get 0

What am I doing wrong, or this a bug?

TIA

Chuck

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That just looks like floating-point representation. It's as rounded as it can get!

-Johann

On Wed, Feb 4, 2015 at 6:22 AM, Chuck Hipschman ckhipschman@gmail.com wrote:

7 / 8.0 roundTo 0.01 = 0.88 Aha! Thanks!

But:

100 * (1.05 raisedTo: 10) roundTo: 0.01 162.89000000000001

"162.88946267774418" "unrounded" 100 * (1.05 raisedTo: 15) roundTo: 0.01 207.89000000000001

"207.8928179411367" "unrounded" Bug, or me again :-)

MacBook Pro (Retina, 15-inch, Early 2013) System Version: OS X 10.10.2 (14C109)

Image

/Users/chuck/Downloads/Squeak-4.5-All-In-One/Squeak-4.5-All-in-One.app/Contents/Resources/Squeak4.5-13680.image Squeak4.5 latest update: #13680 Current Change Set: Unnamed1 Image format 6505 (32 bit)

Virtual Machine

/Users/chuck/Downloads/Squeak-4.5-All-In-One/Squeak-4.5-All-in-One.app/Contents/MacOS/Squeak Croquet Closure Cog VM [CoInterpreter VMMaker.oscog-eem.331] 4.5 Mac OS X built on Aug 22 2013 10:08:05 Compiler: 4.2.1 (Apple Inc. build 5666) (dot 3) platform sources revision VM: r2776 http://www.squeakvm.org/svn/squeak/branches/Cog Plugins: r2545 http://squeakvm.org/svn/squeak/trunk/platforms/Cross/plugins CoInterpreter VMMaker.oscog-eem.331 uuid: 37d2e4b0-2f37-4e2d-8313-c63637785e59 Aug 22 2013 StackToRegisterMappingCogit VMMaker.oscog-eem.333 uuid: 84da9cb8-7f30-4cb7-b4fb-239a11f63b54 Aug 22 2013

On Wed, Feb 4, 2015 at 2:59 AM, Ben Coman btc@openinworld.com wrote:

...

In the interest of teaching how to fish, look at the senders of #roundTo: to find its usage.

I'll post a full answer tomorrow if you don't beat me to it.

cheers -ben

On Wed, Feb 4, 2015 at 4:34 PM, Chuck Hipschman ckhipschman@gmail.com wrote:

...

7 / 8.0 roundTo: 2 I expect 0.88, I get 0

What am I doing wrong, or this a bug?

TIA

Chuck

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Louis LaBrunda <Lou <at> Keystone-Software.com> writes:

Hi Guys,

On Wed, 4 Feb 2015 08:22:02 -0500, Johann Hibschman <johannh <at> gmail.com> wrote:

...

That just looks like floating-point representation. It's as rounded as it can get! -Johann

At first I thought some more parans "(" were needed but that didn't change anything. No this sounds like a bug to me (ar at least something that can be improved) as VA Smalltalk prints 162.89, so somehow they are able to make the floats do the right thing.

Lou

Lou, I'm very suspicious about what VA does. IMO you should not trust too much what you see (what it prints!) Because 16289*0.01 and 162.89 are not really the same float...

(16289*0.01) asFraction printShowingMaxDecimalPlaces: 1074 '162.890000000000014779288903810083866119384765625'

((162.89) asTrueFraction printShowingMaxDecimalPlaces: 1074) '162.8899999999999863575794734060764312744140625'

For having least surprising read-eval-print loops here are 3 levels of expectations: 1) every two different Float shall have a different printString; 2) every Float printString shall be reinterpreted to the same Float; 3) every Float shall be printed to the shortest representation that will be reinterpreted to the same Float. Squeak responds to level-3, so somehow does the right thing.

I suspect VA has lower expectations (only print the first n decimals, even if Float are different, they will print the same...).

The question is why rounding to 0.01?

If it's just to print, then it's better to do so with some instructions like 100 * (1.05 raisedTo: 10) printShowingDecimalPlaces: 2. -> '162.89'

For versatile printing options, I suggest loading NumberPrinter package from http://ss3.gemstone.com/ss/NumberPrinter/

(FloatPrinter fixed) digitCount: 2; print: 100 * (1.05s2 raisedTo: 10) -> '162.89'

If it's for monetary things like computing interests, then the advice is to not use Float but ScaledDecimal.

100 * (1.05s2 raisedTo: 10) roundTo: 0.01s2 -> 162.89s2

Nicolas

On 16.02.2015, at 07:29, Louis LaBrunda Lou@Keystone-Software.com wrote:

That's why I thought there was a problem with #roundTo: but maybe #roundTo: has some other intent that I'm not aware of?

It's used for snapping values to a grid. E.g. in ScrollBar>>setValue:.

- Bert -

On Fri, Feb 13, 2015 at 4:56 PM, nicolas cellier < nicolas.cellier.aka.nice@gmail.com> wrote:

...

If it's for monetary things like computing interests, then the advice is to not use Float but ScaledDecimal.

100 * (1.05s2 raisedTo: 10) roundTo: 0.01s2 -> 162.89s2

Nicolas

So, for money, I would suggest not using ScaledDecimal, but rather

FixedDecimal.

ScaledDecimal can do funny things that you would not expect in real money land:

m := 1/3 asScaledDecimal: 2. m "==> 0.33s2" m + m + m "==> 1.00s2"

You shouldn't be allowed to add 33 cents together and get a whole dollar (usd, at least)!

FixedDecimal actually rounds to the specified length (ScaledDecimal keeps the entire precision 'behind the curtains').

m := 1/3 asFixedDecimal: 2. m "==> 0.33" m + m + m "==> 0.99"

http://www.squeaksource.com/FixedDecimal.html

-cbc