CPU-heavy tasks may not be constrained as much on mutation as on the host VM architecture. The threading system purposefully prevents a thread from hogging all

CPU-heavy tasks may not be constrained as much on mutation as on the host VM architecture. The threading system purposefully prevents a thread from hogging all resources. And since you have to run every computation in a thread (process), there really is some overhead. As I'm sure you know, the BEAM is built for concurrency, not for parallelizing computations. Take Haskell for example, which is also immutable but doesn't require you to spin up processes to do computations. It handles CPU intensive tasks significantly better, but is a worse choice for highly concurrent low latency soft real-time apps because of the scheduler and garbage collector mechanisms. Edit: Btw thanks for bringing up that comparison across types issue. Never realized that. What's your solution to it? I'd write guards on functions that filter input based on types, then have a final fallback with no pattern matching that throws an error explicitly.