Spherical manifolds etc.

[rafaqz]

It would be ideal if GeoData could represent spherical dimensions where the index wraps without a start/end.

And possibly more complex manifolds.

In discussions with @juliohm https://discourse.julialang.org/t/ann-geodata-jl/45502/5
I suggested a Speherical IndexMode to allow spherical indexing and selectors.

This and other similar properties require a new type to dispatch on for index lookup, and also new behaviours of Int getindex that wrap values outside of the axis range back into it.

Probably a better method than a new indexmode Spherical (which uses inheritance) is a composition/trait hybrid, which would be a manually set field for all AbstractSampled index modes. It could be called geometry and return values in Geometry, of Circular and Linear or similar. Other index modes can default to a trait. So:

geometry(mode::IndexMode) = Linear()
geometry(mode::AbstractSampled) = mode.geometry

[rafaqz]

Obviously, indexing into a Circular mode dim with anything other than : would convert it to Linear as it would no longer completely wrap around

[rafaqz]

We have this now with Cyclic lookups