That looks great. One thing I would look for is iterating over multiple matches
in a string. I'd want to see lazy and non-lazy sequences.
let wordMatcher = Regex(":w*") // or whatever matches word-characters
// separated by non-word character.
for w in aString[allMatches: wordMatcher] { print(w) }
for w in warAndPeaceNovel[allMatchesLazy: wordMatcher].prefix(50) {
print(w) }
--
C. Keith Ray
* https://leanpub.com/wepntk <- buy my book?
* http://www.thirdfoundationsw.com/keith_ray_resume_2014_long.pdf
* http://agilesolutionspace.blogspot.com/
> On Jan 11, 2018, at 9:50 AM, John Holdsworth via swift-evolution
> <swift-evolution@swift.org> wrote:
>
> Hi Michael,
>
> Thanks for sending this through. It’s an interesting read. One section gave
> me pause however. I feel Swift should resist the siren call of combining
> Swift Syntax with Regex syntax as it falls on the wrong side of Occam's
> razor. ISO Regex syntax is plenty complex enough without trying to
> incorporate named capture, desirable as it may be. Also, if I was to go down
> that route, I’d move away from / as the delimiter which is a carry over from
> Perl to something like e”I am a regex” to give the lexer more to go on which
> could represent say, a cached instance of NSRegularExpression.
>
> And now for something completely different...
>
> Common usage patterns for a regex fall into 4 categories: deconstruction,
> replacement, iteration and switch/case. Ideally the representation of a regex
> match would the same for all four of these categories and I’d like to argue a
> set of expressive regex primitives can be created without building them into
> the language.
>
> I’ve talked before about a regex match being coded as a string/regex
> subscripting into a string and I’ve been able to move this forward since last
> year. While this seems like an arbitrary operator to use it has some semantic
> sense in that you are addressing a sub-part of the string with pattern as you
> might use an index or a key. Subscripts also have some very interesting
> properties in Swift compared to other operators or functions: You don’t have
> to worry about precedence, they can be assigned to, used as an interator, and
> I've learned since my last email on this topic that the Swift type checker
> will disambiguate multiple subscript overloads on the basis of the type of
> the variable is being assigned to.
>
> An extension to String can now realise the common use cases by judicious use
> of types:
>
> var input = "Now is the time for all good men to come to the aid of the party"
>
> if input["\\w+"] {
> print("match")
> }
>
> // receiving type controls data you get
> if let firstMatch: Substring = input["\\w+"] {
> print("match: \(firstMatch)")
> }
>
> if let groupsOfFirstMatch: [Substring?] = input["(all) (\\w+)"] {
> print("groups: \(groupsOfFirstMatch)")
> }
>
> // "splat" out up to N groups of first match
> if let (group1, group2): (String, String) = input["(all) (\\w+)"] {
> print("group1: \(group1), group2: \(group2)")
> }
>
> if let allGroupsOfAllMatches: [[Substring?]] = input["(\\w)(\\w*)"] {
> print("allGroups: \(allGroupsOfAllMatches)")
> }
>
> // regex replace by assignment
> input["men"] = "folk"
> print(input)
>
> // parsing a properties file using regex as iterator
> let props = """
> name1 = value1
> name2 = value2
> """
>
> var params = [String: String]()
> for groups in props["(\\w+)\\s*=\\s*(.*)"] {
> params[String(groups[1]!)] = String(groups[2]!)
> }
> print(params)
>
> The case for switches is slightly more opaque in order to avoid executing the
> match twice but viable.
>
> let match = RegexMatch()
> switch input {
> case RegexPattern("(\\w)(\\w*)", capture: match):
> let (first, rest) = input[match]
> print("\(first) \(rest)")
> default:
> break
> }
>
> This is explored in the attached playground (repo:
> https://github.com/johnno1962/SwiftRegex4)
> <SwiftRegex4.playground.zip>
>
> I’m not sure I really expect this to take off as an idea but I’d like to make
> sure it's out there as an option and it certainly qualifies as “out there”.
>
> John
>
>> On 10 Jan 2018, at 19:58, Michael Ilseman via swift-evolution
>> <swift-evolution@swift.org> wrote:
>>
>> Hello, I just sent an email to swift-dev titled "State of String: ABI,
>> Performance, Ergonomics, and You!” at
>> https://lists.swift.org/pipermail/swift-dev/Week-of-Mon-20180108/006407.html,
>> whose gist can be found at
>> https://gist.github.com/milseman/bb39ef7f170641ae52c13600a512782f. I posted
>> to swift-dev as much of the content is from an implementation perspective,
>> but it also addresses many areas of potential evolution. Please refer to
>> that email for details; here’s the recap from it:
>>
>> ### Recap: Potential Additions for Swift 5
>>
>> * Some form of unmanaged or unsafe Strings, and corresponding APIs
>> * Exposing performance flags, and some way to request a scan to populate them
>> * API gaps
>> * Character and UnicodeScalar properties, such as isNewline
>> * Generalizing, and optimizing, String interpolation
>> * Regex literals, Regex type, and generalized pattern match destructuring
>> * Substitution APIs, in conjunction with Regexes.
>>
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution@swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>
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