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

Craig Cruden ccruden at novafore.com
Fri Jan 29 03:28:07 CST 2016

So the solution to everything in the proposal is to create a mutable variable and then a bunch of if statements in inverse format?

Then take that and embed in a “pure” function where you need closures?  

And forget about pattern matching and decomposing enums?

And this is the solution to “all”?

> On 2016-01-29, at 16:09:19, James Campbell via swift-evolution <swift-evolution at swift.org> wrote:
> 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 <mailto: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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