Comment (by Wolfgang Kastaun):

The only remaining GSL dependency is monotonic spline interpolation on irregular spaced data. I have already implemented the monotonic spline interpolation for regularly spaced data in another code part, generalizing that is no too much work and I am optimistic to get rid of GSL soon.

The Boost dependency is another matter. I am using a root-finder and ODE integrator from Boost which I don’t want to re-implement. However, those are header-only dependencies, so I think I will try to isolate the required headers and ship them in the repo.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2610/reprimand-thorn-requires-gsl-20-but-does