[Haskell] Top Level <-

Adrian Hey ahey at iee.org
Mon Aug 25 11:55:05 EDT 2008

(Moving to Haskell cafe)

Edward Kmett wrote:
> On Sun, Aug 24, 2008 at 7:12 PM, Ashley Yakeley <ashley at semantic.org> wrote:
>> Is there any interest in implementing a top level "<-" to run monadic code?
> This is actually implemented in jhc. See the 'top level actions' section of
> http://repetae.net/computer/jhc/manual.html

Gosh! I was always quite impressed by Johns determination to write a
Haskell compiler and by his self discipline in resisting the temptation
to fix everything that was wrong with Haskell and keep to standards :-)

I implemented my own ACIO monad a while ago (which is of course quite
useless without top level <- bindings) and it turned out that there
was quite a lot that could go in here.

The only problem seemed to be that some things that seemed perfectly
reasonable to create via ACIO had *IO* finalisers associated with them,
which didn't feel right to me. But if you think about how finalisers
get run I'm inclined to think we should insist that they are ACIO too.

Adrian Hey

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