Pretty sure Array conforms to hashable and ==.
> On Jan 10, 2017, at 23:43, David Sweeris <daveswee...@mac.com> wrote: > > > On Jan 11, 2017, at 01:29, David Sweeris via swift-evolution > <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote: > >> >> On Jan 11, 2017, at 01:11, Freak Show <freaksho...@mac.com >> <mailto:freaksho...@mac.com>> wrote: >> >>> >>>> On Jan 7, 2017, at 23:37, Derrick Ho <wh1pch...@gmail.com >>>> <mailto:wh1pch...@gmail.com>> wrote: >>>> >>>> I think pattern matching is the most compelling reason to keep tuples. >>>> >>>> If they were gone, how would we replace the following? >>>> >>>> switch (a, b) { >>>> case (value1, value2): >>>> case (value3, value4): >>>> } >>> >>> I meant to mention this: Smalltalk - Objective C's mother language - has >>> no switch statement (or 'if' or loops either). The language is incredibly >>> malleable because it only does one thing - send messages to objects and all >>> the language constructs are in the library. It would take very little time >>> to add one. Off and on someone does it as an exercise but it never sticks. >>> >>> Instead, you just use a dictionary of closures. An Objective C equivalent >>> might be: >>> >>> NSDictionary* switch = @{ >>> @[@0,@1]: ^{ NSLog(@"zero one"); }, >>> @[@1,@1]: ^{ NSLog(@"one one"); } >>> }; >>> >>> NSArray* pair = @[@3, @5]; >>> >>> (switch at:pair ifAbsent:^{})(); //where at:ifAbsent: is added in the >>> Smalltalk style as an extension. >>> >>> The Smalltalk equivalent (much less ugly because of the lack of @'s) is >>> >>> switch := { >>> #(0 1) -> [ Transcript nextPutAll: 'zero one' ] . >>> #(1 1) -> [ Transcript nextPutAll: 'one one' ] . >>> #(1 2) -> [ Transcript nextPutAll: 'one two' ] . >>> } asDictionary. >>> >>> (switch at: pair ifAbsent:[ [] ]) value. >>> >>> So its not like this is some kind of key feature. Switch's vs dictionaries >>> of closures - pretty much the same thing as pattern matching goes. The >>> only thing you have to do is put an object at key that identifies itself as >>> equal to the pattern you will throw at it. >> >> I suspect that's a fair bit slower than a switch statement. I'm not in >> front of my computer, so I can't prove it, though. > > Also, Swift's dictionary requires its keys to conform to `Hashable`, which > would mean we'd have to create a formal struct *and* the "==" method for it > would have to act as a pattern matched instead of checking equality. I > suspect this could break a great many things that depend on "Equatable" > meaning what it says. > > - Dave Sweeris (again)
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