[vimes656]

> But the thing is that if they push the "pure" ideology to its limits they will uncover a number of useful things along the way.

For example new elegant approaches to parallelism/concurrency that would be very difficult in an impure language.

[microtonal]

Indeed. For instance, something like

http://hackage.haskell.org/package/parallel-3.1.0.1/docs/Con...

Would be very difficult to implement in a language that is not referentially transparent and lazy.