[swift-evolution] [Discussion] Parentheses

[Joe Groff]

> On Jul 6, 2016, at 7:47 AM, Vladimir.S via swift-evolution <swift-evolution at swift.org> wrote:
> 
> On 06.07.2016 3:57, Jens Persson via swift-evolution wrote:
>> Please feel free to ignore this naive attempt to engage in this discussion.
>> 
>> My understanding of the history of Swift's tuples, argument lists, pattern
>> matching, associated values, etc. in two steps:
>> 
>> 1. Initial Idealism *:
>> Simple powerful heavily reused general concept.
>> 
>> 2. Iterative pragmatism / reality *:
>> Complicated (exceptions to) rules.
>> 
>> (* Inevitably not taking everything in to account.)
>> 
>> Has there been any recent attempts to outline a more or less complete
>> redesign for these things, returning to step 1 so to speak, but taking into
>> account what has now been learned?
>> 
>> 
>> As a side note (and supposedly trivial to most but me):
>> 
>> Parentheses (parenthesized expressions in the grammar?) are used for all of
>> these parts of the language, and they probably should be, but perhaps the
>> similarities and differences between the language constructs can be made
>> clearer to see by pretending that argument and parameter lists are written
>> with eg ≪≫ and tuples with eg ⊂⊃, etc.?
>> 
>> For example, I think most people agree that we should be able to use
>> "sloppy/forgiving" parenthetical grouping in code such as:
>> ((1 + (2 * 3)) * (x + (-5))) - y
>> This is fine and can be used to express meaning for the person
>> reading/writing, even though it means that some of the parens can become
>> superfluous to a machine interpretation.
>> 
>> AFAICS this need not have anything to do with tuples and/or parameter
>> lists, but the fact that Swift is treating eg:
>> func foo(x: ((((Int))))) { print(x) }
>> as
>> func foo(x: Int) { print(x) }
>> and
>> ((Int, Int))
>> as
>> (Int, Int)
> 
> If SE-0110 will be accepted, ((Int, Int)) will mean "1 tuple with Int,Int fields" and (Int, Int) will mean only "list of two Ints in parameters"

((Int, Int)) would still be equivalent to (Int, Int). SE-0110 only concerns parameter lists in function types.

-Joe

> 
>> seems to suggest that it somehow does.
>> 
>> Or maybe I have just forgotten the reasons for why there can be no such
>> thing as (a nested) single element tuple (type).
>> 
>> I also can't remember what the pros & cons of disallowing labeled single
>> element tuples were.
>> 
>> Happy to be corrected and pointed to relevant reading : )
>> 
>> /Jens
>> 
>> 
>> 
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