I realised that in the current implementation, when a number is serialised by STON it is either as an integer literal or as a float literal.

There is a risk to loose precision, especially if what you serialise is a ScaledDecimal or a fraction.

I propose a simple change to fix this:

1. Add STONWriter>>#isInJsonMode method which returns true if the STONWriter wants to write JSON

2. Add:

Fraction>>#stonOn: stonWriter
    stonWriter isInJsonMode
        ifTrue: [ ^ super stonOn: stonWriter ].
    
    stonWriter writeObject: self streamMap: [ :dictionary |
        dictionary at: #numerator put: numerator.
        dictionary at: #denominator put: denominator ]

3. Add:

ScaledDecimal>>#stonOn: stonWriter
    stonWriter isInJsonMode
        ifTrue: [ ^ super stonOn: stonWriter ].
    
    stonWriter writeObject: self streamMap: [ :dictionary |
        dictionary at: #numerator put: numerator.
        dictionary at: #denominator put: denominator.
        dictionary at: #scale put: scale ]