Some more bikeshedding:
Perhaps ffor, as in
ffor = flip fmap
or perhaps
infixr 0 <$$>
(<$$>) = flip (<$>)
xs <$$> \x -> ...
(cf. <**>)
In both cases they should go in Data.Functor
Sjoerd
On Mar 28, 2012, at 11:26 PM, [email protected] 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 <[email protected]> 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.
>>
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--
Sjoerd Visscher
https://github.com/sjoerdvisscher/blog
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