[swift-evolution] [Pitch] Raw mode string literals

[Tony Allevato]

On Thu, Nov 23, 2017 at 12:21 PM Xiaodi Wu via swift-evolution <
swift-evolution at swift.org> wrote:

> On Thu, Nov 23, 2017 at 2:14 PM, John Holdsworth via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>> I’m beginning to wish I hadn’t tied this proposal so strongly to regular
>> expressions!
>> It is indeed the wrong motivation. Even as a ten year veteran of Perl
>> development
>> I’m not sure we want to bake it into the language quite so tightly (isn’t
>> a part of
>> Foundation?) What would /regex/ represent - an instance of
>> NSRegularExpression?
>> Would the flags be pattern options or matching options? This is a whole
>> other debate.
>>
>> For me the focus of raw strings was a sort of super-literal literal which
>> has many
>> applications. The r”literal” syntax has a precedent in Python and there
>> seemed
>> to be a syntactic gap that could be occupied but perhaps there are other
>> alternatives
>> we could discuss. It would be a shame to see ‘quoted strings’ be used for
>> this however.
>> I still live in hope one day it will be used for single character UNICODE
>> values.
>>
>> Since what passes for a single character changes by Unicode
> revision--such as whenever they get around to enumerating the permitted
> modifying attributes of the poop emoji--it is quite impossible (and Swift's
> `Character` doesn't attempt to) to enforce single-characterness at compile
> time. We should put any such notions to rest up front.
>

Unless I'm misunderstanding you here, I don't think that's true: writing
something like `let c: Character = "ab"` is definitely a compile-time
error: https://gist.github.com/allevato/ae267e2aaaa7939d6233d66a87b48fc0

To the original point though, I don't think Swift needs to use single
quotes for single characters (or single scalars). Type inference already
infers Characters from single-character String literals in contexts where a
Character is expected, and the only time you need to be explicit is if
you're trying to resolve an overload or initialize a variable by itself.
Using single quotes to avoid writing "as Character" would feel like a waste.




> On 23 Nov 2017, at 19:10, Brent Royal-Gordon <brent at architechies.com>
>> wrote:
>>
>> On Nov 23, 2017, at 11:15 AM, Chris Lattner via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>
>> Until we figure out that path forward for regex’s, I think they aren’t
>> the right motivation for this proposal.
>>
>>
>> 1. Even in our shining pattern matching future—a future which I, for one,
>> am eager to hasten—we will still need to interoperate with
>> NSRegularExpression and other Perl 5-compatible regex engines.
>>
>> 2. Code generation.
>>
>> 3. Windows-style paths.
>>
>> 4. Doesn’t LaTeX use backslashes?
>>
>> 5. Etc.
>>
>> I think the Motivation section undersells this proposal. Regexes are a
>> strong short-run use case, but in the long run, we’ll need this for other
>> things. In both cases, though, raw literals will be a useful addition to
>> the language, improving the clarity of Swift code much like multiline
>> literals already have.
>>
>> --
>> Brent Royal-Gordon
>> Sent from my iPhone
>>
>>
>>
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