[Haskell-cafe] Re: philosophy of Haskell

Conal Elliott conal at conal.net
Sun Aug 15 06:08:48 EDT 2010

On Sat, Aug 14, 2010 at 10:11 PM, Bill Atkins <watkins at alum.rpi.edu> wrote:

> On Saturday Aug 14, 2010, at 12:50 AM, Conal Elliott wrote:
> > And the IO monad is what Jerzy asked about.  I'm pointing out that the
> state monad does not capture concurrency, and the "EDSL model" does not
> capture FFI.  (Really, it depends which "EDSL model".  I haven't seen one
> that can capture FFI.  And maybe not concurrency either.)
> >
> So which model captures the way the IO monad works?

I don't think anyone has given a denotational (functional-style) model for
the meaning of IO.  As I wrote

IO carries the collective sins of our tribe, as the scapegoat did among the
ancient Hebrews. Or, as Simon Peyton Jones expressed it, “The IO monad has
become Haskell’s sin-bin. Whenever we don’t understand something, we toss it
in the IO monad.” (From Wearing the hair shirt – A retrospective on
Is it likely that we can then come along later and give a compelling and
mathematically well-behaved notion of equality to our toxic waste pile? Or
will it insist on behaving anti-sociably, as our own home-grown Toxic
Avenger <http://en.wikipedia.org/wiki/Toxic_Avenger>?
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