I love how Reagent works and I do think it makes interactive applications simpler and easier to reason about. That said, I think FP still has one disadvantage

I love how Reagent works and I do think it makes interactive applications simpler and easier to reason about. That said, I think FP still has one disadvantage which is performance. This is because the underlying computer is 100% imperative and there are still a lot of work to make FP patterns efficient. FP works well for interactive UIs because the number of objects that change in GUI is very small, so performance is not an issue. But take a video game, for example, then you have thousands of moving objects that are updated at 60FPS. Once you get that you notice is really hard to write the logic as a set of immutable state changes, object allocation becomes a bottleneck and then you discover that OO is more suitable, at least for now. Maybe later there will be ways to efficiently translate the FP patterns into the imperative CPU models.