[reactive] First draft of reactive-tetris

[Conal Elliott]

I believed second == fmap (on pairs) also until very recently.  See

    http://netsuperbrain.com/blog/posts/analysis-of-lazy-stream-programs/
    http://lukepalmer.wordpress.com/2008/10/03/laziness-and-the-monad-laws/

Hm!

- Conal

On Tue, Nov 18, 2008 at 10:41 AM, Robin Green <greenrd at greenrd.org> wrote:

> fmap actually does the same thing as second (when applied to pairs), so
> you can replace second with fmap.
>
> If you want to go insane, you can actually make this redefinition:
>
> import Prelude hiding ((.))
>
> infixr 9 .
> (.) :: (Functor f) => (a -> b) -> f a -> f b
> (.) = fmap
>
> and then just use (.) (either infix or bracketed) instead of fmap
> throughout.
>
> --
> Robin
>
> On Tue, 18 Nov 2008 10:23:37 -0800
> "Conal Elliott" <conal at conal.net> wrote:
>
> > You can also mix in 'first' and 'second' arbitrarily and read them
> > directly from the type as well, when there is (possibly nested) pair
> > structure on the way to the value being modified.  That's why I call
> > fmap, first, and second "semantic editor combinators".  Sometime soon
> > I'm going to blog about these tricks.
> >
> >   - Conal
> >
> > On Tue, Nov 18, 2008 at 10:20 AM, Creighton Hogg <wchogg at gmail.com>
> > wrote:
> >
> > >
> > >
> > > On Tue, Nov 18, 2008 at 12:15 PM, Conal Elliott <conal at conal.net>
> > > wrote:
> > >
> > >> Also, a less forgetful version of subs might be useful:
> > >>
> > >>      withSubs xs e :: [a] -> Event b -> Event (b,a)
> > >>
> > >> and then
> > >>
> > >>     subs xs e  = snd <$> withSubs xs e
> > >>
> > >> or, if you like,
> > >>
> > >>     subs = (fmap.fmap.fmap) snd withSubs
> > >>
> > >> Btw, you can read the three fmaps directly from the signature of
> > >> withSubs (two arrows plus one Event on the way to the pair).
> > >>
> > >>   - Conal
> > >
> > >
> > > That's a cute trick with the number of fmap's required.  Never
> > > thought of it that way.
> > >
> > > Also, I'd like to apologize for not mentioning quicksilver from
> > > #haskell in my last e-mail.  An honest slip-up, but an
> > > inappropriate one.
> > >
> _______________________________________________
> Reactive mailing list
> Reactive at haskell.org
> http://www.haskell.org/mailman/listinfo/reactive
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.haskell.org/pipermail/reactive/attachments/20081118/c97d422f/attachment.htm