[swift-evolution] [Proposal idea] Support for pure functions

[Andrew Bennett]

Hi,

I started another thread on @pure in swift, luckily Chris Lattner reminded
me about this one. I'm going to continue any discussion here so we don't
fragment the conversation.

The other thread was a pre-proposal discussion called "Proposal proposal:
@pure keyword", it isn't archived so I cannot link it.

I've summarised the progress so far here (it's in the proposals directory
for convenience):

https://github.com/therealbnut/swift/blob/therealbnut-pure-preproprosal/docs/proposals/PureKeyword.rst

If I've missed anything or you want to update, clarify, fix typos, etc.
please submit a PR :) I'm trying to keep it focused on things that have
little contention.

I've tried to unify the ideas from both the other thread and this one into
that summary. As it's not really a proposal I haven't included the
excellent justifications that Jimmy initially stated, they can be added if
it becomes a proposal. Please add a PR if you would like them there.


On Tue, Dec 22, 2015 at 9:08 AM, Joe Groff via swift-evolution <
swift-evolution at swift.org> wrote:

>
> > On Dec 21, 2015, at 2:04 PM, Alex Popov via swift-evolution <
> swift-evolution at swift.org> wrote:
> >
> > Slight tangent, would a guarantee of purity also allow for more
> Tail-Call Optimizations? A cursory glance at SO seems to point to TCO not
> always being applied, especially when ARC is involved.
>
>
> I don't think any reasonable meaning for `pure` in Swift would affect the
> possibility of TCO. There was another thread about TCO here you might read
> back on; as I explained there, ARC is not a barrier to TCO, our ownership
> and machine-level calling conventions are. We would need to be able to use
> a specific calling convention for guaranteed-TCOable entry points.
>
> -Joe
>
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160110/020caac4/attachment.html>