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

[Xiaodi Wu]

On Thu, Nov 23, 2017 at 2:47 PM, Tony Allevato <tony.allevato at gmail.com>
wrote:

>
>
> 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
>

Hmm, yes, it still attempts to make a best effort, it seems. I had thought
that this compile-time check was removed altogether, as it cannot be done
in the general case.


> 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.
>
>> Agree.

> 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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>>>
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>
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