[ANN] The STON Specification

STON is able to serialise Pharo’s Floats, what do you mean by double ?

 

Floating-point numbers in IEEE 64-bit format, 14 or 15 significant digits, with a range between =10^307 and 10^307.

 

Additionally, I recently asked Sven if t would be possible to store ScaledDecimals (I think it implements what you call ArbitraryPrecisionFloats) without loss of precision.

 

I’m referring VW’s Double (and SmallDouble in 64-bit engines/images).  APFs are binary representations that can be arbitrarily large, using Integers (LargePositiveIntegers for example) to model the bits of the mantissa.

 

Before, because STON extends JSON, it was storing all kind of numbers either as float or integer.

 

Now, thanks to Sven, STON stores ScaledDecimals correctly (without loss of precision through serialisation as float, what was done before).

 

But I do not know if this change is integrated in recent images yet.

 

…..

 

Number subclass: #Float

                instanceVariableNames: ''

                classVariableNames: 'E Epsilon Halfpi Infinity Ln10 Ln2 MaxVal MaxValLn MinValLogBase2 NaN NegativeInfinity NegativeZero Pi RadiansPerDegree Sqrt2 ThreePi Twopi'

                poolDictionaries: ''

                category: 'Kernel-Numbers'

 

 

My instances represent IEEE-754 floating-point double-precision numbers.  They have about 16 digits of accuracy and their range is between plus and minus 10^307. Some valid examples are:

               

                8.0 13.3 0.3 2.5e6 1.27e-30 1.27e-31 -12.987654e12

….

 

I see that Pharo’s Float is VW’s Double.   So then I just need to be able to serialize APF.

 

….

FIFloatType subclass: #FFIFloat128

                instanceVariableNames: ''

                classVariableNames: ''

                poolDictionaries: ''

                category: 'UnifiedFFI-Types'

 

 

I'm a 128bits (cuadruple precision) float.

It is usually not used, but some compiler modes support it (__float128 in gcc)

 

THIS IS NOT YET SUPPORTED

….

 

The class above is also from the Pharo 7 image.  This is the largest of the c-type FFIFloats.  Any Float classes of this size and larger for the Smalltalk heap on 64-bit Pharo? 

 

 

Cheers,

 

Shaping

 

 

Le 6 nov. 2018 à 06:58, Shaping <[hidden email]> a écrit :

 

(Having domain problems recently.  Please excuse this posting if you have
seen it twice.  I've not seen it appear yet on the list.)


Can STON be extended to handle Doubles and ArbitraryPrecisionFloats?

Shaping

-----Original Message-----
From: Pharo-dev [[hidden email]] On Behalf Of
David T. Lewis
Sent: Wednesday, October 31, 2018 14:58
To: Pharo Development List <[hidden email]>
Subject: Re: [Pharo-dev] [ANN] The STON Specification

This is very clear and well written.

Dave

Hi,

Since there can never be enough documentation I finally took some time
to write a more formal description of STON as a data format.

 https://github.com/svenvc/ston/blob/master/ston-spec.md

The idea is to let this stabilise a bit and to then update the two
other documents describing STON, where necessary:

 https://github.com/svenvc/ston/blob/master/ston-paper.md

https://ci.inria.fr/pharo-contribution/job/EnterprisePharoBook/lastSuc
cessfulBuild/artifact/book-result/STON/STON.html

Also, the latest changes in STON have to make their way to the Pharo
image as well.

 https://github.com/svenvc/ston

All feedback is welcome.

Sven


--
Sven Van Caekenberghe
Proudly supporting Pharo
http://pharo.org
http://association.pharo.org
http://consortium.pharo.org