[swift-evolution] [Proposal] Set literal and Set type syntax

[Howard Lovatt]

Thanks for the correction and I agree that removing the argument label
would be a good idea.

On Tuesday, 19 January 2016, Liam Butler-Lawrence <liamdunn at me.com> wrote:

> Set("a", "b", "c”) doesn’t compile. It currently has to be  Set(arrayLiteral:
> "a", "b", "c”). That said, I’d be satisfied with removing the external
> parameter name “arrayLiteral”. Not only is it unnecessary, but it’s
> confusing too: variadic parameters are not the same as an Array.
>
> Liam
>
> On Jan 18, 2016, at 5:43 PM, Howard Lovatt via swift-evolution <
> swift-evolution at swift.org
> <javascript:_e(%7B%7D,'cvml','swift-evolution at swift.org');>> wrote:
>
> Sorry -1 from me. Doesn't seem worth it. Not much wrong with Set("a", "b",
> "c").
>
> On Tuesday, 19 January 2016, Seth Friedman via swift-evolution <
> swift-evolution at swift.org
> <javascript:_e(%7B%7D,'cvml','swift-evolution at swift.org');>> wrote:
>
>> I dig the idea of Sets having a literal syntax, rather than continuing to
>> be the ugly stepchild of CollectionTypes. I'm not sure, though, that this
>> particular literal syntax is very obvious. While the Array and Dictionary
>> syntaxes are similar enough to many other languages in which arrays and
>> maps exist, I might be confused if I saw your proposed syntax in Swift.
>>
>> Not to mention that it's not the prettiest syntax, but that's more
>> subjective.
>>
>> On Mon, Jan 18, 2016 at 1:24 PM, Michael Henson via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>
>>> Swift currently has literal and type shorthand syntax for native Array
>>> and Dictionary types, but not the Set type. It would be useful to have a
>>> literal shorthand for Set as well.
>>>
>>> The existing productions for array and dictionary literals and types
>>> share brackets as delimiters, differing only in the contents between the
>>> brackets. That poses a slight problem for Set because any syntax, to be
>>> useful, must also be easily distinguishable from the other types.
>>>
>>> Consider that Arrays and Dictionaries are both naturally indexed
>>> collections. Arrays by the integer value of the order of items in the
>>> collection, usually implicitly, and Dictionaries by the hashed key
>>> associated with each value.
>>>
>>> Arrays, implicit index:
>>>
>>> let array = ["a", "b", "c"]
>>> var array: [String]
>>> var empty: [String] = []
>>>
>>> Dictionaries, explicit index:
>>>
>>> let dictionary = ["a": 1, "b": 5, "c": 9]
>>> var dictionary: [String: Int]
>>> var empty: [String: Int] = [:]
>>>
>>> Sets, by contrast, have no particular order and no "key". Even though
>>> the Set is enumerable and iterable, it isn't indexed. With that in mind, we
>>> can declare that a Set literal or Set type literal should distinguish
>>> itself by declaring that it has no index.
>>>
>>> The Set literal could be:
>>>
>>> let set = [ _: "a", "b", "c" ]
>>> var set = [ _: String ]
>>> var empty: [ _: String ] = [_:]
>>>
>>> In the grammar:
>>>
>>> set-literal -> [ _ : array-literal-items[opt] ]
>>> literal-expression -> array-literal | dictionary-literal | set-literal
>>>
>>> set-type -> [ _ : type ]
>>> type -> array-type | dictionary-type | set-type | ... etc.
>>>
>>>
>>> Examples:
>>>
>>> let x = [ _: "A", "B", "C" ]
>>> let y: [ _: String ] = [ _: ]
>>>
>>>
>>> Alternatives considered:
>>>
>>> Without literals, declaring a Set type is straightforward, easy to
>>> recognize, and not much more verbose. There might not be enough of a
>>> difference to justify special syntax in the core language.
>>>
>>> Mike
>>>
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution at swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>>
>>>
>>
>>
>> --
>> Seth Friedman
>> *Software Development Engineer II*
>> *Amazon.com <http://amazon.com>*
>>
>
>
> --
>   -- Howard.
>
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>
>

-- 
  -- Howard.
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