[swift-evolution] Tuple conversion and type composition

[Chris Lattner]

> On Feb 7, 2016, at 8:12 AM, Patrick Gili via swift-evolution <swift-evolution at swift.org> wrote:
> 
> What about using << to denote concatenation? Many languages use this operator to denote "append", which is essentially concatenate.

Random comment: the swift approach is generally to define new operators for new operations.  We really don’t like the C++ approach of overloading existing operators to mean different things in different contexts.

-Chris

> 
> -Patrick
> 
>> On Feb 6, 2016, at 5:41 PM, Andrew Bennett via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> Thanks Tino, it would be good to come up with some alternatives for +.
>> 
>> I was initially thinking `(Int,Int) (Int,Int)` without operators. However I think this could potentially be a mistake. I like + as it's familiar with array operators.
>> 
>> As for the prevalence of tuples in the language, every function and value in Swift has a tuple in it. The associated values in an enum are a tuple. They are everywhere.
>> 
>> For some more examples have a look at the linked proposal :)
>> 
>> 
>> On Sun, Jan 31, 2016 at 11:28 PM, Tino Heth <2th at gmx.de <mailto:2th at gmx.de>> wrote:
>>> I'd like a a way to concatenate tuple types together:
>>> 
>>> typealias ABCD = (A,B)+(C,D) // Same as (A,B,C,D)
>> 
>> I don't like the use of "+" for concatenation, but giving more power to tuples would be neat… you just need to find examples with convincing motivation ;-)
>> Obviously, the value of tuple-operation increases with the prevalence of tuples in language and libraries, so I wouldn't be surprised if their importance rises in the future (and maybe we can think of nice ways to combine tuple-related ideas).
>> 
>>> Also a way to allow tuples to be converted to other tuples that are the same when flattened:
>>> 
>>> (a,(b,c),d) as ((a,b),(c,d))
>> It would be cool if such a concept ("compiler, please check if those two types have a compatible memory-layout, and if that is the case, let me use them interchangeable when I tell you to do so) could be extended to structs — that could solve the problem of different implementations of fundamental types nicely.
>> 
>> That leads me to an unrelated thought:
>> It seems to me there is a duality between methods and closures on one side, and structs and tuples on the other — tuples feel very much like anonymous structs (restricted by the fact that you cannot add methods like custom getters & setters). It's not related to you proposal, but I wonder if there are implications visible from this point of view...
>> 
>> Tino
>> 
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