Joe Duffy's "Thoughts on immutability and concurrency"

[Jesse Phillips]

Andrei Alexandrescu Wrote:

> This blog entry looks interesting:
> 
> http://www.bluebytesoftware.com/blog/PermaLink,guid,7a57f623-d65d-4212-973d-29bdcf61dd3a.aspx
> 
> Andrei

I must not be understanding something in his use of immutability. For his spellchecker example he suggested making a copy of some portion of the document into an immutable data-structure so that it can be shared without locks or copying. How is this better than message passing of mutable data?

I suppose you can then pass this immutable structure to a spellchecker, grammar analyzer, and a haiku generator without multiple memory copies? In which case you're still assuming shared memory across threads or programs.