I view the need to use the reducer functions in place of the "vanilla" versions similarly to a compiler flag (you could stick it in the namespace definition and

I view the need to use the reducer functions in place of the "vanilla" versions similarly to a compiler flag (you could stick it in the namespace definition and not worry about it for the rest of the code). In my mind, what makes this "automatic" is that in at least 80% of the cases, that's the only thing you would need to do. All of your code using map, reduce, and friends can remain mostly unchanged. Before reducers, I'd have said that Obj-C's blocks with GCD was the closest thing to "automatic parallelization" (in that you could get concurrent execution without the need to handle explicit concurrency primitives). The problem, of course, is that writing C/Obj-C with closures is a non-trivial shift in design. With Clojure, the way that code is currently written is already well positioned to benefit from reducers.