> On Jan 7, 2017, at 23:37, Derrick Ho <[email protected]> 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.
_______________________________________________
swift-evolution mailing list
[email protected]
https://lists.swift.org/mailman/listinfo/swift-evolution
