Price handling in Vuu

[stonesmi]

Until now, the example apps have used Double for all floating point types. However I believe that we need to offer something with more precision (similar to Java BigDecimal) for Prices and Notional amounts in particular.

I see a few options here:

1. Add support for a Decimal type, directly backed by a Java BigDecimal in the Data table. There are fewer options to move these into off heap memory though (future enhancement)

2. Add support for a Decimal type, backed by a Long. The Long would need to be divided by 10^X to convert to decimal format on the UI for display and multiplied back for filtering / RPC. Another downside is we are limiting ourselves to a max Integer value based on how many decimal places we offer. Upside is that we already support Long.

3. Write our own impl of BigDecimal as a Record of two Longs, one for the Integer and one for the mantissa.

4. Alternatively, we just live with Doubles.

[stonesmi]

@heswell @chrisjstevo @tanjjj

[stonesmi]

As discussed today, we have agreed to try following the same mechanism as Apache Avro:

https://avro.apache.org/docs/1.8.1/spec.html#Decimal

We will use a fixed scale of 6 for the mantissa. 8 was considered but is only applicable for Japanese Yen and we have no use case for that at present.

For example:

TODO