Smalltalk float to currency how to ?

Hi all,

I have Float in form:
12.0
123.3453
etc
and want to format it to two-digits-after-dot.
Searched through classes but found nothing suitable except

n := 12.6.
String streamContents: [:s|
 n absPrintOn: s base: 10 digitCount: n asInteger asString size + 2.
]

while it works fine for any float like 12.3245
it does not add zero to float like 12.6 :-(
I would like to see 12.60

Is there simple way to do it ?
like fprintf in C/Perl world ?

Thanks.
-Dmitry.
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> I would like to see 12.60
>
> Is there simple way to do it ?
> like fprintf in C/Perl world ?
>
Try this.
(amount * 100) asInteger printStringAsCents.



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Michel Bany wrote:
>
>> I would like to see 12.60
>>
>> Is there simple way to do it ?
>> like fprintf in C/Perl world ?
>>
> Try this.
> (amount * 100) asInteger printStringAsCents.

Also, you might consider using an integer number of cents or even a
Money class to represent money, rather than a float. Floating point
arithmetic doesn't produce the kind of results you'd expect for money...
if you know this already, just ignore me.

Colin

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Try this ;-)


[ :float :digit  | | s |
        float = 0
                ifTrue: [ s := (String new: digit+1) atAllPut: $0 ]
                ifFalse: [ s := (float*(10**digit)) asInteger printString ].
        (s copyFrom: 1 to: (s size - digit)) , '.' , (s copyFrom: (s size
-digit+1) to: s size) ]
                        value: 0.0
                        value: 2



Dmitry Dorofeev wrote:

--
-------------------------
Luc Damas
Assistant professor
Condillac, LISTIC, ESIA
University of Savoie
France
http://ontology.univ-savoie.fr/luc.damas

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Dmitry Dorofeev wrote:
> Hi all,
>
> I have Float in form:
> 12.0
> 123.3453
> etc
> and want to format it to two-digits-after-dot.
> Searched through classes but found nothing suitable except

In a 3.8 derived image, I get:

12.0 printShowingDecimalPlaces: 2. ==> '12.00'
123.3453 printShowingDecimalPlaces: 2. ==> '123.35'

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What about the compatibility between Squeak and VW?


> In a 3.8 derived image, I get:
 >
 >
> 12.0 printShowingDecimalPlaces: 2. ==> '12.00'
> 123.3453 printShowingDecimalPlaces: 2. ==> '123.35'
>

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Michel Bany wrote:

>
>> I would like to see 12.60
>>
>> Is there simple way to do it ?
>> like fprintf in C/Perl world ?
>>
> Try this.
> (amount * 100) asInteger printStringAsCents.
>

If 'amount' is, say, 12.499999, I think 12.50 is the desirable answer.  
The above will instead yield 12.49.

Nevin

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Luc Damas wrote:
>
> What about the compatibility between Squeak and VW?
>
>> In a 3.8 derived image, I get:
>
>> 12.0 printShowingDecimalPlaces: 2. ==> '12.00'
>> 123.3453 printShowingDecimalPlaces: 2. ==> '123.35'
>>

A compatibility package - you're going to need one eventually
if you need to run in both environments. If Squeak is your
mainline then you'll need a SqueakCompatibility in VW,
and vice versa.

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Luc Damas a écrit :

>
> What about the compatibility between Squeak and VW?
>
>
With Seaside loaded, this should work in both :
(amount * 100) rounded printStringAsCents.

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I had the same need, so I added this message in Float :
----------
roundedTo: precision
        "Answer the float truncated at precision decimal"
        (self rounded = self)
        ifTrue: [ ^ self rounded ]
        ifFalse: [ ^ (((self * (10 raisedTo: precision)) rounded) / (10
raisedTo: precision)) asFloat ]
----------
It's working fine for me.

Florian

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Thanks,

this one looks practical.
I am sad there is no Money in Squeak though...

Yanni Chiu wrote:
>
>
> In a 3.8 derived image, I get:
>
> 12.0 printShowingDecimalPlaces: 2. ==> '12.00'
> 123.3453 printShowingDecimalPlaces: 2. ==> '123.35'
>
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in Wed, Feb 01, 2006 at 02:51:42PM +0300, Dmitry Dorofeev wrote:
> Thanks,
>
> this one looks practical.
> I am sad there is no Money in Squeak though...

Don't be sad, there is ScaledDecimal in Squeak :)

Float is *not* appropriate for financial calculations, but
ScaledDecimal should be OK. And #printShowingDecimalPlaces: will
work with ScaledDecimal also:

123.3453 asScaledDecimal printShowingDecimalPlaces: 2. ==> '123.35'

Dave

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Thanks for tip, it is very helpful for a newbie like me.

Also, isn't it boring to see a list of suggestions for selector name
when you type in your implementation of renderContentOn: something like

self renderConfirmationOn: html.

and save changes ?

I'd like Squeak to create a missed selector for me and open it for edit (if save successful).
Now I just accept my choice (click on renderConfirmationOn: in popup menu)
select 'renderConfirmationOn: html' with a mouse + Alt+C click, Alt+V
and only after that I can edit selector body.

I hope the practical benefit of this feature is enough to excite someone :-)

-Thanks,
Dmitry

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Thanks for tip, it is very helpful for a newbie like me.

Also, isn't it boring to see a list of suggestions for selector name
when you type in your implementation of renderContentOn: something like

self renderConfirmationOn: html.

and save changes ?

I'd like Squeak to create a missed selector for me and open it for edit (if save successful).
Now I just accept my choice (click on renderConfirmationOn: in popup menu)
select 'renderConfirmationOn: html' with a mouse + Alt+C click, Alt+V
and only after that I can edit selector body.

I hope the practical benefit of this feature is enough to excite someone :-)

-Thanks,
Dmitry

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Hi,

Assuming I have prices with 2 digits after dot I want to calculate VAT
with 4 digits precision. VAT May be shown still rounded to 2 digits,
but some clients want to see even 4 digits after dot !!! With high
turn over made from small sells it is some real money due to rounding errors :-)

I made some tests and found a funny example:

a := ScaledDecimal newFromNumber: 6.18 scale: 4.
b :=  ScaledDecimal newFromNumber: 5 scale: 4.
a / b   1.2359s4
a / b printShowingDecimalPlaces: 4 '1.2360'
6.18 / 5.0  1.236

why a / b shows 2.2359s4 ?
but (a / b printShowingDecimalPlaces: 4) shows correct answer
It makes me nervious....

Thanks.

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Hi,

I guess this is how ScaleDecimal prints itself. See printOn: in ScaleDecimal
>> instance.
BTW, if u comment last 2 lines in  that method, you get the desired effect.

Best regards,
Valdas Bucinskas

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Dmitry
Dorofeev
Sent: Thursday, February 02, 2006 4:14 PM
To: The Squeak Enterprise Aubergines Server - general discussion.
Subject: [Seaside] Money ScaledDecimal is it really *appropriate* ?


Hi,

Assuming I have prices with 2 digits after dot I want to calculate VAT
with 4 digits precision. VAT May be shown still rounded to 2 digits,
but some clients want to see even 4 digits after dot !!! With high
turn over made from small sells it is some real money due to rounding errors
:-)

I made some tests and found a funny example:

a := ScaledDecimal newFromNumber: 6.18 scale: 4.
b :=  ScaledDecimal newFromNumber: 5 scale: 4.
a / b   1.2359s4
a / b printShowingDecimalPlaces: 4 '1.2360'
6.18 / 5.0  1.236

why a / b shows 2.2359s4 ?
but (a / b printShowingDecimalPlaces: 4) shows correct answer
It makes me nervious....

Thanks.

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Yes, there's a bug when converting Floats to Scaled Decimals. It's  
not precise. This works:

a := ScaledDecimal newFromNumber: 618/100 scale: 4.
b := ScaledDecimal newFromNumber: 5 scale: 4.
a / b "1.2360s4"

This is the problem:

        6.18 asFraction

        (869757678035927/140737488355328)

instead of
       
        (6.18 * 10e4) rounded / 10e4

        (309/50)

So when converting from a Float it should be rounded to scale, IMHO.

You should report this (best along with the fix) on the squeak bug  
tracker. And because it's not a Seaside problem, we should continue  
the discussion to squeak-dev.

- Bert -

Am 02.02.2006 um 15:13 schrieb Dmitry Dorofeev:


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Dmitry Dorofeev wrote:
I'd like to second what I believe Colin said about using integers to
represent money.  If you need four digits then that dictates the scale
of your integers.  Maybe ScaledDecimals would do the job, don't know
anything about them, but my experience dictates that it only takes 10
minutes to put together a Money (and/or Currency) class based on this
integer representation and it is well worth the effort.  Attached is one
that I've used in the past...maybe not as robust as you need but you
could probably hack it into your 4-digit form faster than you could
learn about ScaledDecimal...

Maybe somewants to post a more industry hardened version :-)

David


'From Squeak3.7 of ''4 September 2004'' [latest update: #5989] on 2 February 2006 at 12:26:34 pm'!
Magnitude subclass: #Money
        instanceVariableNames: 'cents'
        classVariableNames: ''
        poolDictionaries: ''
        category: 'Grocery-Domain'!

!Money methodsFor: 'accessing' stamp: 'cds 3/27/2005 13:31'!
cents
        ^cents! !


!Money methodsFor: 'comparing' stamp: 'cds 3/27/2005 13:35'!
< other
        ^self cents < other cents! !

!Money methodsFor: 'comparing' stamp: 'cds 2/2/2006 12:26'!
= other
        ^self species = other species and: [self cents = other cents]! !

!Money methodsFor: 'comparing' stamp: 'cds 3/27/2005 13:35'!
hash
        ^self cents hash! !


!Money methodsFor: 'arithmetic' stamp: 'cds 3/27/2005 13:36'!
+ other
        ^Money cents: self cents + other cents! !


!Money methodsFor: 'initialize-release' stamp: 'cds 3/27/2005 13:31'!
cents: anObject
        cents := anObject! !


!Money methodsFor: 'printing' stamp: 'cds 3/27/2005 19:03'!
printOn: aStream
        aStream nextPutAll: '$'.
        self cents // 100 printOn: aStream.
        aStream nextPut: $..
        self cents \\ 100 < 10 ifTrue: [aStream nextPut: $0].
        cents \\ 100 printOn: aStream.! !

"-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- "!

Money class
        instanceVariableNames: ''!

!Money class methodsFor: 'instance creation' stamp: 'cds 3/27/2005 13:30'!
cents: anInteger
        ^self new cents: anInteger; yourself! !

!Money class methodsFor: 'instance creation' stamp: 'cds 4/4/2005 12:49'!
zero
        ^self cents: 0! !

'From Squeak3.7 of ''4 September 2004'' [latest update: #5989] on 2 February 2006 at 12:26:48 pm'!

!Integer methodsFor: '*Grocery' stamp: 'cds 3/27/2005 14:04'!
cents
        ^self asMoney! !

'From Squeak3.7 of ''4 September 2004'' [latest update: #5989] on 2 February 2006 at 12:28:26 pm'!
TestCase subclass: #MoneyTest
        instanceVariableNames: ''
        classVariableNames: ''
        poolDictionaries: ''
        category: 'Grocery-Tests'!

!MoneyTest methodsFor: 'tests' stamp: 'cds 3/27/2005 14:06'!
testAddition
        | m1 m2 |
        m1 := 532 cents.
        m2 := 654 cents.
       
        self assert: (m1 + m2) cents = (532 + 654)! !

!MoneyTest methodsFor: 'tests' stamp: 'cds 3/27/2005 14:04'!
testCreation
        | m |
        m := 100 asMoney.
        self assert: m cents = 100.
       
        m := 100 asDollars.
        self assert: m cents = 10000.
       
        m := Money cents: 10.
        self assert: m cents = 10.
       
        m := 965 cents.
        self assert: m cents = 965! !

!MoneyTest methodsFor: 'tests' stamp: 'cds 3/27/2005 19:02'!
testPrinting
        self assert: 965 cents printString = '$9.65'.
        self assert: 430 cents printString = '$4.30'.
        self assert: 502 cents printString = '$5.02'! !

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On Feb 2, 2006, at 9:29 AM, David Shaffer wrote:
I wouldn't call it industry hardened, but I've posted what we use in  
Dabble to http://squeaksource.com/Money .  It uses the MoneyBag  
approach to dealing with currency that I remember seeing as a pattern  
somewhere...

Avi

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Heh, I wondered how long it'd be before someone said just use a Money
object, this is Smalltalk after all.
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