I didn't say that side-effect-free program kernels are "less interesting" - I said they were beside the point of this post. (But I do think they're very cool a

I didn't say that side-effect-free program kernels are "less interesting" - I said they were beside the point of this post. (But I do think they're very cool and important in their own right!) The GHC developers' point was that restricted side effects are necessary for automatic parallelization. Your answer seems to be, "I can parallelize languages with unrestricted side-effects... in sections where you restrict yourself to a side-effect-free subset." Yes, I'm happy when a C++ compiler automatically optimizes my inner loop. But I'd rather be able to use "par" at the highest level of my program, and parallelize anything from XML parsing to physics simulation, without worrying that some library call ten functions down the stack will turn out to be non-reentrant.