[Haskell-cafe] Re: I love purity, but it's killing me.

[Paul L]

BTW, I doubt the (cyclic) sharing problem relates that much to purity,
because in an impure language (or the unsafe observable sharing), you
still have to remember whether something has been traversed or not and
in the worst case accumulates everything that's been traversed so far
before releasing all of them in the end. If you remember the history
by mutating some states, e.g., using a dirty tag, you lose the ability
to do simultaneous traversals.

Adding a simple indirect reference only to the places where sharing is
needed (and thus making it explicit) could alleviate this problem. But
this solution exists in both pure and impure languages.

So let's love purity still :-)

-- 
Regards,
Paul Liu

Yale Haskell Group
http://www.haskell.org/yale