Add interface for optionally static size

[mateuszbaran]

Basic infrastructure for solving JuliaManifolds/Manifolds.jl#625 .

[codecov]

Codecov Report

Merging #160 (c35a1be) into master (71f85b6) will decrease coverage by 0.12%.
The diff coverage is 100.00%.

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src/DefaultManifold.jl	100.00% <100.00%> (ø)
src/maintypes.jl	100.00% <100.00%> (ø)

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[kellertuer]

Nice that you started this.

While I think this is quite technical and should not concern beginners, it might be nice for advanced usages.
A small benchmark illustrating when which is nicer might be nice as well (if that can be well-illustrated)

[mateuszbaran]

While I think this is quite technical and should not concern beginners, it might be nice for advanced usages.
A small benchmark illustrating when which is nicer might be nice as well (if that can be well-illustrated)

Yes, it's definitely not for beginners.
Benchmarks would be hard at the moment because all good examples live in Manifolds.jl. I think rotation matrices would make a great example for a benchmark.

[kellertuer]

Sure let's just keep that a bit in mind to explain this feature with a benchmark somewhen.
I think I see advantages of both and disadvantages, but having a small tutorial on that would be great – sure probably only in Manifolds.jl

[mateuszbaran]

Sure, I will add a clear explanation with an example in the Manifolds.jl PR that converts key manifolds to AbstractSize.