Rich Hickey's slides from jvm lang summit - worth a read?

[Lutger]

Walter Bright wrote:

> Executive summary: pure functions and immutable data structures help
> manage program complexity.

I think so too, but you left out the time and identity part related to stm 
and multiversion concurrency. You could argue these notions are a possible   
consequence of immutable data structures and pure functions. But the time 
thingy somehow seems more fundamental than that. 

Anyhow it nicely hints at what we can do with these concepts. It seems to me 
that this is the fundamental part of functional programming, and not 
functions as first class citizens. This is also the part that most modern 
languages that claim to be hybrid OO / functional do not support.