Transition from Rational to HalfInteger

jagot commented 5 years ago

In many places, Rationals are being used for angular momenta. These can be more efficiently represented by HalfInteger from WignerSymbols.jl. E.g Term would simply be

struct Term
    L::HalfInteger
    S::HalfInteger
    parity::Parity
end

jagot commented 5 years ago

We should also ask @Jutho to export the HalfInteger interface.

Jutho commented 5 years ago

You mean a simple export HalfInteger in WignerSymbols.jl? I am certainly fine with that.

mortenpi commented 5 years ago

Would you also consider some minor API additions? I have a version of your HalfInteger with some updates in one of the PRs. I would be more than happy to prepare a PR against WignerSymbols.

It is mainly just a few additional methods, such as multiplication with integers and string parsing.
I also found it handy to have a HalfIntegerRange type, mirroring UnitRange, so that you could write e.g. HalfInteger(-10) : HalfInteger(10). Not sure if that is appropriate for WignerSymbols.
If I may, I might also suggest a small change to how the constructor behaves. I find it more intuitive if HalfInteger(n) == n not HalfInteger(n) == n // 2.

Jutho commented 5 years ago

Yes I am open to such changes and would probably benefit from them as well. The most Julian choice for the constructor was also something I was wondering about.

JuliaAtoms / AtomicLevels.jl

Transition from Rational to HalfInteger #7