[swift-evolution] Proposal: Pattern Matching Partial Function (#111)

James Campbell james at supmenow.com
Fri Jan 29 03:09:19 CST 2016

I think all of this could be solved by just having postfix if statements

var str: String?

str = "hot" if state == .Hot
str = "cold" if state == .Cold

//if the ??= operator proposal is accepted then we could just do:
str ??= "Invalid Temperature"

This is used a lot in Ruby, more flexible since it could be used on any line of code, flexible and concise. I think it reads quite well so beginners will grasp it easily (as I did when writing my first Ruby)

I think compiler wise it could be treated like a do while loop except it only loops once ;) 

Sent from my iPhone

> On 29 Jan 2016, at 08:06, Charles Constant via swift-evolution <swift-evolution at swift.org> wrote:
> Sorry for the barrage here, Paul :)
> > I’m not even convinced the new syntax is clearer so much as cleverer.
> As I've followed the various threads for switch-like assignments, I've been thinking a lot about how valid it is to say that more explicit is all that helpful to beginners. I wish I had the resources to test these assumptions with actual people who had never written Swift.
> As an example. 
> We assume that this:
>     let phrase: String
>     switch( temperature ) {
>         case .Cold: str = "Too cold"
>         case .Hot:  str = "Too hot"
>         default:    str = "Just right"
>     }
> is going to be easier for beginners than something like this:
>     let phrase = temperature ?
>         "Too cold" if .Cold :
>         "Too hot” if .Hot :
>         "Just right" if _  
> I'm using a short version here that is not the actual proposal, and that we won't use (since we don't want to overload "if"). But I have a strong hunch that a beginner is not going to find the longer version any more clear. There's a lot of syntax for the programmer to parse in the "switch" statement, as it stands. I suspect the less redundancy we have, the easier it is to figure out what is going on.
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