astGrad VS Squants

I mean that article of yours highlights the difficulties one encounters fairly well, I would say. I don't disagree that this is (generally) a tricky problem!

Nim allows you to do a lot, e.g. derivatives of a unitful expression with measurement errors [0]. But other aspects run into the reality of dealing with a static type system. For example in Measuremancer [1], the library handling measurements with uncertainties, each `Measurement` is a single generic `Measurement[T]`. Each measurement stores the derivatives for error propagation. Obviously the derivatives have different units. Now, we could make `Measurement` a two-fold generic, `Measurement[T, U]`, but that just makes things more unwieldy in practice, for not much gain.

Without rewriting a majority of existing code you will always run into trouble where your perfect unit type system will either break or you'll need to work around it anyway (e.g. calling into some C library for part of the code).

[0]: https://github.com/SciNim/astGrad#extra-fun

[1]: https://github.com/SciNim/Measuremancer/

Scala's squants library is a nice implementation of units-of-measure/dimensional-analysis http://www.squants.com

In particular it uses types for dimensions; whilst units are just constructors. Hence `Meters(2)` and `Microns(7)` have the same type (`Length`).

squants for the “Market” package to use in financial calculations.

take a peek at https://www.squants.com looks like not in your language, but maybe you can apply some same concepts

You might find the Squants library for Scala interesting; it even seems like an apt usage of some oft-questioned language features.

https://github.com/typelevel/squants