Rounding modes

[dpsanders]

This is a very nice package, congrats!

However, to use this as a drop-in replacement for Float64 and BigFloat in the context ofIntervalArithmetic.jl, it would be necessary to be able to do operations with given rounding mode, e.g.

+(x, y, RoundDown)
sin(x, RoundUp)

I suspect that this is a Hard Problem, but just thought I should record it.
cc @JeffreySarnoff

[saschatimme]

This is definitely a hard problem and I really don't see a straightforward way to achieve this at the moment. But I agree that it is good to record it.