[Haskell-cafe] IO and Wash

John Goerzen jgoerzen at complete.org
Wed Feb 16 09:30:29 EST 2005

On Wed, Feb 16, 2005 at 07:31:07AM +0100, Tomasz Zielonka wrote:
> > verbatim.  Any ideas?
> I have never used table_io. maybe there's a bug in it. Hmmm, it seems
> to be conceptually wrong. The single purpose of table_io seems to be
> to avoid keeping the result of an IO action in the log. But how is
> WASH going to recreate it when it's needed again as in your example?

Ahh, I think I understand what you're saying...  table_io is not
supposed to be unsafe; that is, it should work without saving data in
the log even if the input would be different on a different session.
But yes, if the validation fails, there would be no way to do that save
re-reading the input.

It sounds like, in my case, unsafe_io would be better.  My input should
never change across a single session.

The next question is this: the I/O really only needs to be done once.
Once the user has selected an item, that's enough.  If my understanding
is correct, on each subsequent screen in my application, Wash will
follow through the entire call history, and will run the I/O again even
if not needed.  Is that correct?  Or does the unsafe_io prevent that?

Thanks for all your help.  I appreciate it and apologize for being so
dense about Wash.

-- John

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