[swift-evolution] renaming CustomStringConvertible

Xiaodi Wu xiaodi.wu at gmail.com
Fri Jul 1 14:47:41 CDT 2016


How do you mean?
On Fri, Jul 1, 2016 at 14:44 David Sweeris <davesweeris at mac.com> wrote:

> Maybe... It's just a property, though. I *think* if something's moving
> into the Syntax thing, I'd rather look for a way to move string
> interpolation there. Maybe.
>
> - Dave Sweeris
>
> On Jul 1, 2016, at 14:24, Xiaodi Wu via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Perhaps another candidate for sinking into `Syntax`?
> On Fri, Jul 1, 2016 at 14:23 Dmitri Gribenko via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>> On Fri, Jul 1, 2016 at 12:16 PM, Eric Habberstad via swift-evolution
>> <swift-evolution at swift.org> wrote:
>> >
>> > To the Swift community,
>> >
>> > May I put forth a couple of new names for the following protocol:
>> >
>> >
>> > - CustomStringConvertible  —   rename as ‘Descriptive’ or as
>> ‘Revealable’
>> >
>> >
>> > Two goals for Swift is clarity and joy in use of the language, so I
>> strongly
>> > feel that ‘Custom-‘ not be part of any new name here since it
>> contributes
>> > little except verbosity
>>
>> Hi Eric,
>>
>> This protocol was called Printable before, but it caused a lot of
>> confusion for developers, and was guiding the developers toward
>> writing incorrect APIs.  We have seen a lot of developers writing code
>> like this:
>>
>> func printAll(_ values: [Printable]) {
>>   for v in values { print(v) }
>> }
>>
>> This code is unnecessarily restrictive since in Swift everything can
>> be converted into a String.
>>
>> func printAll(_ values: [Any]) {
>>   for v in values { print(v) }
>> }
>>
>> The same goes for retrieving debug descriptions and mirrors.  Any
>> value can do that.  It is just that some values can opt into
>> customizing this behavior.
>>
>> Thus, we renamed the protocols, adding the Custom~ prefix.  Our
>> intention was to encourage only conformances to these protocols, and
>> discourage writing APIs against them.
>>
>> Dmitri
>>
>> --
>> main(i,j){for(i=2;;i++){for(j=2;j<i;j++){if(!(i%j)){j=0;break;}}if
>> (j){printf("%d\n",i);}}} /*Dmitri Gribenko <gribozavr at gmail.com>*/
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