[swift-evolution] [Pitch] Support for pure functions. Part n + 1.

[T.J. Usiyan]

There shouldn't be a need for a third arrow with regard to purity. Impure
encompasses pure in that there is simply no guarantee of purity with an
impure function. You should be able to use a pure function in place of an
impure function without any issue whatsoever.

On Fri, Feb 17, 2017 at 1:35 PM, Adrian Zubarev via swift-evolution <
swift-evolution at swift.org> wrote:

> My suggestion is that -> would be the conditional arrow that can be both
> *pure* or *impure*. That would make @pure func foo(_ f: @pure (Int) ->
> Int) -> Int equivalent to func foo(_ f: (Int) ~> Int) -> Int. Plus
> depending on the implementation the compiler *might* be able to help and
> tell you that foo could use ~> instead.
>
>
>
> --
> Adrian Zubarev
> Sent with Airmail
>
> Am 17. Februar 2017 um 19:25:41, Anton Zhilin (antonyzhilin at gmail.com)
> schrieb:
>
> Just let
>
> @pure func foo(_ f: (Int) -> Int) -> Int
>
> be the same as those two combined:
>
> @pure func foo(_ f: @pure (Int) -> Int) -> Int
> func foo(_ f: (Int) -> Int) -> Int
>
> No need for anything like “re-pure” or ≃>.
> ​
>
>
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