[daanx]

In practice, I have not (yet) found many great use cases for the distinction in Koka. It is nice to have "total" functions, but "pure" (exceptions+divergence) is still a good thing (and what Haskell gives you). And like you say, in practice we can easily have functions that just take a long long time to compute.

Still, it is a good extra check and I can see more use for the `div` effect for future verification tools where total functions can be used as a predicates (but non-terminating ones cannot).

[skybrian]

Good to know. At compile or verification time, it seems like you could get the same problem again, though? We want our compiles to finish promptly, and a slow, total predicate could hang.

Which is to say, a possibly-diverging function seems okay to use even by a verification tool, so long as it finishes quickly in practice. Having some notion of analysis-time-safe predicates seems useful but it doesn't seem to map cleanly to being able to prove termination?