[swift-evolution] Proposal: Always flatten the single element tuple

Susan Cheng susan.doggie at gmail.com
Tue Jun 6 22:27:45 CDT 2017

```it's also clear that these code will never be ambiguous

[(1, 2)].map({ \$0 }) // \$0 always not a tuple, because arguments should be
flattened

2017-06-07 11:21 GMT+08:00 Susan Cheng <susan.doggie at gmail.com>:

>  [(1, 2)].map({ x, y in x + y })  // this line is correct
>  [(1, 2)].map({ tuple in tuple.0 + tuple.1 })  // this line should not
> accepted
>
> or
>
>  [(1, 2)].map({ \$0 + \$1 })  // this line is correct
>  [(1, 2)].map({ \$0.0 + \$0.1 })  // this line should not accepted
>
> it's because `((Int, Int)) -> Int` always flatten to `(Int, Int) -> Int`
> so, it should only accept the function with two arguments
>
>
>
> 2017-06-07 11:07 GMT+08:00 Stephen Celis <stephen.celis at gmail.com>:
>
>> I like this a lot, but how do we solve for the function case?
>>
>>     func add(_ x: Int, _ y: Int) -> Int {
>>       return x + y
>>     }
>>
>> Where does `map` with a function of `((Int, Int)) -> Int` fit in?
>>
>> > On Jun 6, 2017, at 10:15 PM, Susan Cheng via swift-evolution <
>> swift-evolution at swift.org> wrote:
>> >
>> > Introduction
>> >
>> >
>> > Because the painful of SE-0110, here is a proposal to clarify the tuple
>> syntax.
>> >
>> > Proposed solution
>> >
>> > 1. single element tuple always be flattened
>> >
>> > let tuple1: (((Int))) = 0  // TypeOf(tuple1) == Int
>> >
>> > let tuple2: ((((Int))), Int) = (0, 0)  // TypeOf(tuple2) == (Int, Int)
>> >
>> > 2. function arguments list also consider as a tuple, which means the
>> function that accept a single tuple should always be flattened.
>> >
>> > let fn1: (Int, Int) -> Void = { _, _ in }
>> >
>> > let fn2: ((Int, Int)) -> Void = { _, _ in }  // always flattened
>> >
>> > let fn3: (Int, Int) -> Void = { _ in }  // not allowed, here are two
>> arguments
>> >
>> > let fn4: ((Int, Int)) -> Void = { _ in }  // not allowed, here are two
>> arguments
>> >
>> > _______________________________________________
>> > swift-evolution mailing list
>> > swift-evolution at swift.org
>> > https://lists.swift.org/mailman/listinfo/swift-evolution
>>
>>
>
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```