# [swift-users] Changing precedence of / operator for my protocol?

Rick Mann rmann at latencyzero.com
Tue Nov 29 20:06:11 CST 2016

```> On Nov 29, 2016, at 16:23 , Jacob Bandes-Storch <jtbandes at gmail.com> wrote:
>
> You could also define a ** exponentiation operator, i.e. "kilogram * meter / second**2".

Oh, good idea! Although I may use a carat. It also will simply s*s to s<sup>2</sup>, eventually.

>
> On Tue, Nov 29, 2016 at 4:15 PM, Rick Mann via swift-users <swift-users at swift.org> wrote:
>
> > On Nov 29, 2016, at 15:22 , Howard Lovatt <howard.lovatt at gmail.com> wrote:
> >
> > Why not define some other symbol so that you can get the precedence you want?
>
> I could, but I think I'll just leave things as they are. No need to add confusion; it works to use parentheses.
>
> >
> >   -- Howard.
> >
> > On 30 November 2016 at 09:28, Greg Parker via swift-users <swift-users at swift.org> wrote:
> >
> > > On Nov 29, 2016, at 2:55 AM, Rick Mann via swift-users <swift-users at swift.org> wrote:
> > >
> > > Working on dimensional analysis, I have some proof-of-concept code that seems to be working:
> > >
> > >    let n1 = kilogram * meter / second * second
> > >    ([(kg⋅m) / s]⋅s)
> > >
> > >     let n2 = kilogram * meter / (second * second)
> > >    [(kg⋅m) / (s⋅s)]
> > >
> > > Note: () around unit products, [] around unit quotients.
> > >
> > > I'd like to adjust the precedence of operator * for my Unit protocol to be higher than /. Is that possible? It wasn't at all clear to me how to do that in Swift 3, or if can even be done at all.
> >
> > You can't. A Swift operator's precedence is the same for all types that implement that operator. Operators * and / cannot use the same precedence on Int but different precedence on Unit.
> >
> > You could try to change the precedence of * and / globally - they're defined like any other operator in stdlib/public/core/Policy.swift - but you'll break lots of other code that way.
> >
> >
> > --
> > Greg Parker     gparker at apple.com     Runtime Wrangler
> >
> >
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> > swift-users at swift.org
> > https://lists.swift.org/mailman/listinfo/swift-users
> >
>
>
> --
> Rick Mann
> rmann at latencyzero.com
>
>
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--
Rick Mann
rmann at latencyzero.com

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