[Haskell-cafe] Re: Where do I put the seq?

David Leimbach leimy2k at gmail.com
Thu Aug 20 10:34:24 EDT 2009

On Thu, Aug 20, 2009 at 2:52 AM, Jules Bean <jules at jellybean.co.uk> wrote:

> Peter Verswyvelen wrote:
>> Not at all, use it for whatever you want to :-)
>> I'm writing this code because I'm preparing to write a bunch of tutorials
>> on FRP, and I first wanted to start with simple console based FRP, e.g.
>> making a little text adventure game, where the input/choices of the user
>> might be parsed ala parsec, using monadic style, applicative style, and
>> arrows, and then doing the same with FRP frameworks like
> This is a really bad place to start a FRP tutorial IMO.
> The interface for 'interact' does not make any promises about the relative
> evaluation order of the input list / production order of the output list.
> That's why you are having to play horrible tricks with seq to try to force
> the order to be what you want.
> I don't think this is the basis of a robust system or a sensible tutorial.
> Just my 2c.

Interesting feedback, but I don't get the reason really.  How is using seq a
"horrible trick"?  It's there for strict evaluation when you need it, and in
this case it was warranted.

And as far as saying it's not a good basis for a robust system, I'm also not
sure I agree, but a "sensible tutorial", that I could believe as I think
it's actually quite difficult to explain these topics to people in a way
they're going to understand right away.

Could we perhaps bother you to suggest an alternative along with your
criticism?  It would feel a little more constructive at least (not that I
think you were being terribly harsh)

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