Is dofib pure or not?Food for thought:
1. The easy but limited solution is that this code doesn't compile, because argumentProvider must have a single type/effect and you couldn't have both a pure and an impure function with that type/effect.
2. Is purity that important? Ultimately we care about avoiding our programs doing unintended things, and often effects are just fine as long as they don't misbehave in some way. Purity is a means to an end.
3. It's fascinating to extend the ideas of generic programming from mainstream type systems to effect systems. I suspect there is a lot of potential benefit to be had if we can figure out how to do this without introducing a lot of boilerplate code, in the same way that we can write code using generic types to various degrees today but have type inference spare us a lot of keyboard bashing.
