Haskell also has a `comparing` function
comparing :: (Ord a) => (b -> a) -> b -> b -> Ordering
which applies a function on both the left hand side and the right hand side to
get two values that can be compared/ordered.
This makes the call site look something like this:
sortBy (comparing length) names
The same can be done in Swift, resulting in a similar and very English-like
calls site:
names.sort(by: comparing { $0.characters.count })
That said. While this (the `comparing` function) is a fun exercise in higher
order functions, a more Swifty syntax for this is probably a separate overload
of the sort/ed/ function.
- David
> On 17 Aug 2016, at 02:17, Silvan Mosberger via swift-evolution
> <[email protected]> wrote:
>
>> I'd be in favor. We'd need another name, since the current closure predicate
>> is already standardized to `by:`.
>
> Haskell uses "on" for sorting with a mapping. There are both
>
> sortOn <> :: Ord
> <http://hackage.haskell.org/package/base-4.9.0.0/docs/Data-Ord.html#t:Ord> b
> => (a -> b) -> [a] -> [a]
>
> and
>
> sortBy <> :: (a -> a -> Ordering
> <http://hackage.haskell.org/package/base-4.9.0.0/docs/Data-Ord.html#t:Ordering>)
> -> [a] -> [a]
>
> in Haskell.
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