[swift-evolution] Changing the curried static methods

[Joe Groff]

> On Mar 12, 2016, at 1:46 PM, Brandon Williams via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Right now instance methods on a type get a curried, static method for free, e.g. CGRect.insetBy is a curried function CGRect -> (CGFloat, CGFloat) -> CGRect. This is super cool and great for code reusability. 
> 
> Unfortunately, I think the order of the curry makes it difficult to use most of the time. With the above example you would use it as such:
> 
> CGRect.insetBy(rect)(10.0, 10.0)
> 
> That doesn’t read very nicely, and it’s more likely that you know (10.0, 10.0) before you know rect, hence you would want to call it as:
> 
> CGRect.insetBy(10.0, 10.0)(rect)
> 
> In general, I would expect a method:
> 
> struct A {
>   func method <B, C> (b: B) -> C
> }
> 
> to have a static method of the form
> 
> A.method: B -> A -> C
> 
> Does this make sense? Is there a reason for the current design that I’m not seeing?

Note that there's a proposal open to flatten away the currying altogether:

https://github.com/apple/swift-evolution/blob/master/proposals/0042-flatten-method-types.md

I agree that it would often be more useful to bind the non-self arguments first. Maybe we could provide a different shorthand for that, though; a number of people for instance have suggested `.insetBy(10.0, 10.0)` as a possibility.

-Joe
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