On 29 March 2012 22:03, Sjoerd Visscher <sjo...@w3future.com> wrote: > Some more bikeshedding: > > Perhaps ffor, as in > > ffor = flip fmap > > or perhaps > > infixr 0 <$$> > (<$$>) = flip (<$>) > > xs <$$> \x -> ...
I don't think it makes sense to add a whole new operator for that. You can just use sections: (<$> xs) \x -> ... The reason you can't do this with <*> is the ordering of effects. I have to admit, though, that the above isn't exactly readable. The non-operator version is somewhat more readable: (`map` xs) \x -> ... I'd still prefer "for" or "foreach". > > (cf. <**>) > > In both cases they should go in Data.Functor > > Sjoerd > > On Mar 28, 2012, at 11:26 PM, e...@ezrakilty.net wrote: > >> I would very much like to see a standard function for "flip map" along >> these lines. I think it would make a lot of code more readable. >> >> Like the OP, I use "for" in my own code. It's unfortunate that >> Data.Traversable takes the name with another type. Two options would be >> to (a) reuse the name in Data.List and force people to qualify as >> necessary, or (b) choose another name for "flip map". >> >> Regarding other possible names: forall is a keyword and forAll is used >> by QuickCheck. One possibility would be "foreach". >> >> Ezra >> >> On Wed, Mar 28, 2012, at 10:19 PM, Christopher Done wrote: >>> On 28 March 2012 22:05, Matthew Steele <mdste...@alum.mit.edu> wrote: >>>> Doesn't for already exist, in Data.Traversable? Except that for = >>>> flip traverse. >>> >>> Traverse doesn't fit the type of fmap, it demands an extra type >>> constructor: >>> >>> traverse :: (Traversable t,Applicative f) => (a -> f b) -> t a -> f (t b) >>> >>> fmap :: Functor f => (a -> b) -> f a -> f b >>> >>> Note the (a -> f b) instead of (a -> b). >>> >>> E.g. >>> >>> fmap :: (a -> b) -> [a] -> [b] >>> >>> can't be expressed with traverse, you can only get this far: >>> >>> traverse :: (a -> [b]) -> [a] -> [[b]] >>> >>> Unless I'm missing something. >>> >>> _______________________________________________ >>> 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 >> > > -- > Sjoerd Visscher > https://github.com/sjoerdvisscher/blog > > > > > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe -- Push the envelope. Watch it bend. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
