Re: Re: [Haskell-cafe] Looking for pointfree version
import Control.Applicative data Pair a = a :*: a instance Functor Pair where f `fmap` (x :*: y) = f x :*: f y instance Applicative Pair where (f :*: g) * (x :*: y) = f x :*: f y The last f needs to be a g. pure x = x :*: x pointfree :: (a - b - c) - Pair a - Pair b - Pair c --pointfree o x y = pure o * x * y pointfree = ((*) .) . (*) . pure -- in the applicative paper notation: --pointfree o x y = [| o x y |] Very nice. Aside: I wonder how much work it would be to extend the pointfree tool to infer such equalities? -- View this message in context: http://www.nabble.com/Looking-for-pointfree-version-tp21913653p22027350.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Looking for pointfree version
And then to down = mconcat [downPar, downNew, downTrans] Which is pretty cute considering that the original formulation is equivalent to and a tiny tweak away from down p = mconcat [downPar p, downNew p, downTrans p] Hooray for Monoid! - Conal On Mon, Feb 9, 2009 at 6:31 AM, Wouter Swierstra w...@cs.nott.ac.uk wrote: snip How about using Data.Monoid: down = downPar `mappend` downNew `mappend` downTrans Wouter ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Looking for pointfree version
On Thu, Feb 12, 2009 at 6:46 PM, Kim-Ee Yeoh a.biurvo...@asuhan.com wrote: On the same note, does anyone have ideas for the following snippet? Tried the pointfree package but the output was useless. pointwise op (x0,y0) (x1,y1) = (x0 `op` x1, y0 `op` y1) $ pointfree '(\op (a, b) (c, d) - (a `op` c, b `op` d))' (`ap` snd) . (. fst) . flip flip snd . ((flip . (ap .)) .) . flip flip fst . ((flip . ((.) .)) .) . (flip = (((.) . flip . (((.) . (,)) .)) .)) 'Useless' is a bit understated , IMO. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Looking for pointfree version
On Mon, 9 Feb 2009, Edsko de Vries wrote: Hi, Is there a nice way to write down :: Focus - [Focus] down p = concat [downPar p, downNew p, downTrans p] down = concat . sequence [downPar, downNew, downTrans] given the Reader like Monad instance of ((-) a). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Looking for pointfree version
On the same note, does anyone have ideas for the following snippet? Tried the pointfree package but the output was useless. pointwise op (x0,y0) (x1,y1) = (x0 `op` x1, y0 `op` y1) Edsko de Vries wrote: Perfect! Beautiful. I was hoping there'd be a simple solution like that. Thanks! On 9 Feb 2009, at 14:31, Wouter Swierstra wrote: How about using Data.Monoid: down = downPar `mappend` downNew `mappend` downTrans -- View this message in context: http://www.nabble.com/Looking-for-pointfree-version-tp21913653p21971304.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Looking for pointfree version
Hi, Is there a nice way to write down :: Focus - [Focus] down p = concat [downPar p, downNew p, downTrans p] in point-free style? (In doesn't make much difference what these functions do; if it helps, their types are downPar, downNew, downTrans :: Focus - [Focus]). Ideally, I would like to write something like down = downPar ... downNew ... downTrans but I'm not sure what should be on the dots. This works: down = concat . flip map [downPar, downNew, downTrans] . flip ($) but is extremely ugly and doesn't really explain what's going on :) (It seems to me I should be able to take advantage of the list monad, somehow). Pointers appreciated! Edsko ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Looking for pointfree version
On Mon, 9 Feb 2009 14:18:18 + Edsko de Vries devri...@cs.tcd.ie wrote: Hi, Is there a nice way to write down :: Focus - [Focus] down p = concat [downPar p, downNew p, downTrans p] in point-free style? I think this should work: down = concat . swing map [downPar, downNew, downTrans] swing is defined at http://www.haskell.org/haskellwiki/Pointfree#Swing -- Robin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Looking for pointfree version
snip How about using Data.Monoid: down = downPar `mappend` downNew `mappend` downTrans Wouter ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Looking for pointfree version
Rewriting it to: concatMap ($ p)[downPar , downNew , downTrans ] gives: ($ p) = [downPar, downNew, downTrans] didn't check though! =@@i Edsko de Vries schreef: Hi, Is there a nice way to write down :: Focus - [Focus] down p = concat [downPar p, downNew p, downTrans p] in point-free style? (In doesn't make much difference what these functions do; if it helps, their types are downPar, downNew, downTrans :: Focus - [Focus]). Ideally, I would like to write something like down = downPar ... downNew ... downTrans but I'm not sure what should be on the dots. This works: down = concat . flip map [downPar, downNew, downTrans] . flip ($) but is extremely ugly and doesn't really explain what's going on :) (It seems to me I should be able to take advantage of the list monad, somehow). Pointers appreciated! Edsko ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Looking for pointfree version
Perfect! Beautiful. I was hoping there'd be a simple solution like that. Thanks! On 9 Feb 2009, at 14:31, Wouter Swierstra wrote: snip How about using Data.Monoid: down = downPar `mappend` downNew `mappend` downTrans Wouter ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
