Same here. I can handle chaining conditions and narrowing things down, but once there's a De Morgan's filter on the thing, there's just too much state to juggle because what's in front of my eyes is not a refresher for what I actually need to remember ("ok, it says `n < 0`…(De Morgan filter)…n is positive" is too much IMO).
That said, I feel it's really down to double+ negation being hard to handle. `if` with a single negation is fine; `unless` is automatically a negation, so you're just off to a bad start on that front. I feel like the only viable use is in a case like Rust's `let … else { diverge }` where anything that fails the condition is guaranteed to diverge (typically, return) and I can just ignore it when reading the overall codeflow. But Ruby mixes that up and does `diverge unless …` which puts the diverging part "up front" and "in the way" for such readings.
That said, I feel it's really down to double+ negation being hard to handle. `if` with a single negation is fine; `unless` is automatically a negation, so you're just off to a bad start on that front. I feel like the only viable use is in a case like Rust's `let … else { diverge }` where anything that fails the condition is guaranteed to diverge (typically, return) and I can just ignore it when reading the overall codeflow. But Ruby mixes that up and does `diverge unless …` which puts the diverging part "up front" and "in the way" for such readings.