I have, after reading through the whole of "The End of Error" (I'd recommend it even if his plans have changed).
The problem with the unum 1.0 design is that to efficiently implement the scratchpad in software, you need a lot of type-level numerical computation, which Rust doesn't have right now.
unum 2.0 is a significantly simplified design. However, my hunch is that they tried to do a hardware implementation, or at least considered it, and found several limitations or points of unnecessary complexity which they addressed.
While an implementation based on lookup tables may work well in hardware, it can be difficult to optimize in software. Still, they may be useful for comparing with a hardware (FPGA?) implementation, for validity and benchmarking.
I haven't had the time to put into an actual implementation (other than some old sketches I hadn't pushed to GitHub, before realizing the type-level complexity involved), but I've discussed several points on IRC (#rust-offtopic).
I also got the
unum crate registered (in retrospect, prematurely).
If anyone wants to approach further development, I'd be glad to help with whatever I can.