Ficus is a library of Fast, Immutable Collections, mostly based on tree structures.
Coming soon. For the moment, consider this an alpha release, suitable for testing with. Do not use this in production yet.
It starts with F as so many projects do, and it's the name of many different kinds of trees. Plus, there were no other major projects using the name Ficus that I could find, so there was no chance of confusion.
Once this code is stable and well-tested, I plan to submit the RRBVector implementation to FSharpx.Collections. You can help that along by downloading the Ficus NuGet package, testing it, and reporting any bugs you find.