[swift-evolution] ternary operator ?: suggestion

[Paul Ossenbruggen]

	let num = color.map {
		.Red: 100, 
		.Green:  200, 
		.Blue: 300,
		_ : -1 
	}

I am liking this more and more. even if we need to have the cases out front. Just need the case syntax. 

	let num = color.map {
		case .Red: 100, 
		case .Green:  200, 
		case .Blue: 300,
		default: -1 
	}
 
> On Jan 9, 2016, at 5:25 PM, Paul Ossenbruggen <possen at gmail.com> wrote:
> 
> By the way my example should be read the question mark as, transform or map, 
> 
> 	let num = color ? 
> 		.Red to 100 : 
> 		.Green  to 200 : 
> 		.Blue to 300 : 
> 		default  to -1 
> 
> 	let num = color map
> 		.Red to 100 : 
> 		.Green  to 200 : 
> 		.Blue to 300 : 
> 		default  to -1 
> 
>> On Jan 9, 2016, at 5:16 PM, Paul Ossenbruggen <possen at gmail.com <mailto:possen at gmail.com>> wrote:
>> 
>> 
>> 
>> 
>>> On Jan 9, 2016, at 4:09 PM, Charles Constant <charles at charlesism.com <mailto:charles at charlesism.com>> wrote:
>>> 
>>> More fiddling... any takers for "on"? 
>>> 
>>> Yes, this is partly a last ditch attempt trying to revive my earlier proposal :) It still irks me that we'd have a switch using the colon two different ways. Also my last suggestion had the order reversed ( i.e.: "val =test" but then "==test val" in the cases ) which is irritating.
>>> 
>>> 	let str = boo ? 
>>> 		"yes" on true : 
>>> 		"no" on false
>>> 
>>> 	let num = color ? 
>>> 		100 on .Red : 
>>> 		200 on .Green : 
>>> 		300 on .Blue  : 
>>> 		-1 on default 
>>> 
>> 
>> This does have some nice properties, like more compact than “case", don’t need the word “case" out front and a separator. Having the order the other way though I think would not work. You would need t support long expressions etc, so I don’t think having it reversed would be popular. Perhaps something like this
>> 
>> 	let num = color ? 
>> 		.Red to 100 : 
>> 		.Green  to 200 : 
>> 		.Blue to 300 : 
>> 		default  to -1 
>> 
>> I like some of it but, I still want to put the colons in-between the case labels. This syntax would be seen as too different from something we already have with the “case label: expression” syntax. Maybe seen as “different but not better"
>> 
>> Meanwhile I have been learning Scala. The unary function, partial functions, and pattern matching stuff looks cool.
>> 
>> - Paul 
>> 
>>> 
>>> The more verbose forms will be easier to learn, I suppose, but it's also nice, when you have a long list of things like this, to keep things as json-y as possible. Granted if we use the short version, there's developers who will flame anyone listening for doubling down on the evil ternary.
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> On Fri, Jan 8, 2016 at 11:18 AM, Chris Lattner <clattner at apple.com <mailto:clattner at apple.com>> wrote:
>>> On Jan 7, 2016, at 12:10 AM, Paul Ossenbruggen <possen at gmail.com <mailto:possen at gmail.com>> wrote:
>>> > Just a few hopefully quick questions:
>>> >
>>> > Do you have any thoughts on supporting two forms? Like the compact form where case and default are not present, and the more formal switch like form?
>>> 
>>> Adding two forms seems very unlikely to be accepted - even adding one form is unclear :-)
>>> 
>>> > Do you have any specific reasons to not support “where”? Is it just to keep it simple and when we need more complexity use the statement form?
>>> 
>>> I don’t have a strong objection to where, other than trying to keep things simple.  It is reasonable to argue that removing “where” makes things more complex by making the expression *different* from the statement though.
>>> 
>>> -Chris
> 

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