I've been puzzling over what can be done to support this in more widely-used languages. The dilemma relative to the current language ecosystem is that languages with "modern" type systems (Haskell, Rust, Scala, etc) capable of supporting compile-time unit checking, in the particular style I've been exploring, are not yet widely used.
With respect to Java, a couple approaches are plausible. One is to enhance the language, for example with Java-8 compiler plugins. Another might be to implement a unit type system similar to squants <https://github.com/typelevel/squants>. This style of unit type system is not as flexible or intuitive as what can be done with Scala's latest type system sorcery, but it would allow the community to build out a Java native type system that supports compile-time unit analysis. And its coverage of standard units could be made very good, as squants itself demonstrates. Python would also be a high-coverage target. I'm even less sure what to do for python, as it has no compile-time type checking, but perhaps a squants-like python class system would add value. Maybe python's new type-hints feature could be leveraged? Regarding unit expression representation, I'm not unhappy with what I've prototyped in `coulomb-avro`, in broad strokes. It has deficiencies that would need addressing. It doesn't yet support standard unit abbreviations, nor does it understand plurals (e.g. it can parse "second" but not "seconds"). Since it's "unit" field is just a custom metadata key, there is no enforcement. Parsers are currently instantiated via explicit lists of types, which is a property I like, but that may not work well in a world where multiple language bindings must be supported in a portable manner. On Sat, Jun 29, 2019 at 1:46 AM Niels Basjes <ni...@basj.es> wrote: > Hi, > > I attended your talk in Berlin and at the end I thought "too bad this is > only Scala". > > I think it's a good idea to have this in Avro. > > The details will be tricky: How to encode the units in the schema for > example. > Especially because of the automatic conversion you spoke about. > > Niels > > On Fri, Jun 28, 2019, 23:58 Erik Erlandson <eerla...@redhat.com> wrote: > > > Hi Avro community, > > > > Recently I have been experimenting with avro schema that are extended > with > > a "unit" field. By "unit" I mean expressions like "second", or > "megabyte" - > > that is "units of measure". > > > > I delivered a short talk on my experiments at Berlin Buzzwords, which can > > be viewed here: > > https://www.youtube.com/watch?v=qrQmB2KFKE8 > > I also wrote a short blog post that may be faster to ingest: > > > > > http://erikerlandson.github.io/blog/2019/05/23/unit-types-for-avro-schema-integrating-avro-with-coulomb/ > > > > I received some audience interest in making this concept "first class" > for > > avro, and so I'm writing to see what the avro dev community thinks of the > > idea. One issue is that this kind of unit checking is currently only > > available for Scala (and specifically scala 2.13 +). > > > > The Scala project itself is here: > > https://github.com/erikerlandson/coulomb > > > > Cheers, > > Erik > > >
