[swift-evolution] ternary operator ?: suggestion

[J. Cheyo Jimenez]

"or we could go with an optional “then” for statements as was suggested by
Thorsten. "

I don't think this should go in the proposal. An else is alway required in
a guard statement, an expression should not return an optional imho.



On Sunday, December 13, 2015, Paul Ossenbruggen via swift-evolution <
swift-evolution at swift.org> wrote:

>
>
> On Dec 13, 2015, at 8:11 AM, Jakob Egger <jakob at eggerapps.at
> <javascript:_e(%7B%7D,'cvml','jakob at eggerapps.at');>> wrote:
>
> I really don't like the "if cond then expr1 else expr2".
>
> 1) First of all, it's extremely verbose. It's almost as bad as the SQL
> construct "case when cond then expr1 else expr2 end”.
>
>
> Yeah it adds a few characters overall. What used to be 2 chars now takes
> 10. Clarity is preferred though by many. I head frequently people telling
> users to never use ternary operators because they are confusing to read.
>
>
> 2) It makes Swift harder to learn. Newcomers will be confused why you
> sometimes need to use curly braces and why at other times you need to use
> the "then" keyword.
>
>
> I did mention this in Alternatives Considered section. By making the else
> part required, this emphasizes that it is different or we could go with an
> optional “then” for statements as was suggested by Thorsten.
>
>
> 3) It doesn't help when you want to do multi-line calculations
>
>
> This is the case with the ternary as well, I think it is better to keep it
> simple.
>
>
> But there is one good side to this proposal: it nests more naturally than
> the ternary operator:
> "if cond then expr1 else if cond2 then expr2 else expr3"
> vs.
> "cond ? expr1 : (cond2 ? expr2 : expr3)
>
> The proposed syntax for the switch statement is so confusing that I really
> don't think it is a good idea.
>
>
> Not sure why that is, it is essentially the same as the existing switch
> statement except everything is an expression instead of statements. Is
> there anything I can do in the examples or documentation to make things
> clearer?
>
>
> Why not just allow normal if statements to return values?
> I don't see what's so bad about the following:
> "let value = if cond {expr1} else {expr2}"
>
> This would also extend to multiple lines:
> let value = if cond {
>   expr1
> } else {
>   let something = Object()
>   something.doStuff()
>   something
> }
>
>
> I answered this with others, also notice how there are braces everywhere?
> does that really work when you just want to put something on one line. What
> happens when one of your branches returns void? Expressions are guaranteed
> to have a result, statements don’t make such a guarantee.
>
>
>
> Jakob
>
> On 13 Dec 2015, at 06:54, Paul Ossenbruggen via swift-evolution <
> swift-evolution at swift.org
> <javascript:_e(%7B%7D,'cvml','swift-evolution at swift.org');>> wrote:
>
> Hello All,
>
> Been sick in bed all day, but decided to try to be productive…
>
> I did a rough draft of a proposal for implementing if expressions and
> switch expressions based upon the discussions we had here. I have tried to
> keep the scope of the changes as small as possible,  only added one keyword
> and kept things as similar to the existing language constructs as possible.
> If anyone wants to help me with this, or has feedback, please let me know,
>
> https://github.com/possen/swift-evolution/blob/master/0020.md
>
> Thanks,
> - Paul
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20151213/d484b5ae/attachment.html>