[swift-evolution] ternary operator ?: suggestion

[Jo Albright]

Just a couple of thoughts swirling in my brain. 

1. Ternary means : composed of three parts …. if we add case functionality, it no longer is a ternary and should be renamed (ex : nil coalescing … was used instead of calling it a ternary optional). Would love to hear thoughts on what names it could have … if the proposal moves forward.

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I am leaning towards this pattern (someone else introduced), yet I don’t feel it is perfect.

let val = color ?  .Red: 0xFF0000, .Green: 0x00FF00,  .Blue: 0x0000FF,   _: 0xFFFFFF

2. I have a problem with “_”. I don’t agree with it being the default value. It is currently used to discard or ignore values … using it as a default will add unnecessary confusion that does not align with Swift. Writing out the word default instead of _ is only 6 more characters. Please correct me if I am wrong on this note.

let val = color ?  .Red: 0xFF0000, .Green: 0x00FF00,  .Blue: 0x0000FF,   default: 0xFFFFFF

3. Having “?” for the Bool operator and “:” for the cases presents confusion with the current ? : ternary design pattern. This is another potential issue … just not a big of a deal as the “default as _”.

let val = color case .Red: 0xFF0000, .Green: 0x00FF00,  .Blue: 0x0000FF,   default: 0xFFFFFF
let val = color ???  .Red: 0xFF0000, .Green: 0x00FF00,  .Blue: 0x0000FF,   default: 0xFFFFFF

And some less serious ones.

switch let val = color case .Red: 0xFF0000, .Green: 0x00FF00,  .Blue: 0x0000FF,   default: 0xFFFFFF
case let val = color ??? .Red: 0xFF0000, .Green: 0x00FF00,  .Blue: 0x0000FF,   default: 0xFFFFFF

I do believe this functionality is worth adding to Swift core lib. I just want to see it as closely aligned with Swift as possible.

 Nerd . Designer . Developer
Jo Albright
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