Hey everyone,
I would like to pitch an implementation of Regex in Swift and gather all of
your thoughts.
Motivation:
In the String Manifesto for Swift 4, addressing regular expressions was not in
scope. Swift 5 would be a more fitting version to address the implementation of
Regex in Swift. NSRegularExpression is a suitable solution for pattern matching
but the API is in unfitting for the future direction of Swift.
Implementation:
The Regular expression API will be implemented by a Regex structure object
which is a regular expression that you can apply to Unicode strings. The Regex
struct will conform to the RegexProtocol, which is a type that can represent a
regular expression. ExpressibleByRegexLiteral will be used to initialize a
regex literal creating an easy to use syntax and a Match structure will be used
to represent a match found with a Regex.
Draft of implementation:
protocol ExpressibleByRegexLiteral {
associatedtype RegexLiteralType
init(regexLiteral value: Self.RegexLiteralType)
}
// Structure of information about a match of regex on a string
struct Match {
var regex: Regex
var start: String.Index
var end: String.Index
}
protocol RegexProtocol {
init(pattern: String) throws
var pattern: String { get } // string representation of the pattern
func search(string: String) -> Bool // used to check if a match is found at
all in the string
func match(string: String) -> [Match] // returns an array of all the matches
func match(string: String, using: ((Match) -> Void)) // enmuerate over
matches
}
struct Regex: RegexProtocol {
init(pattern: Regex, options: Regex.Options)
let options: [Regex.Options]
static let word: Regex // \w
// other useful regexes can be added as well
}
// Examples
let regex = \[a-zA-Z]+\
let matches = regex.match("Matching words in text.")
for match in matches {
print("Found a match at in string at \(match.start) to \(match.end)")
}
let helloStr = "Hello world"
Regex.word.match(helloStr) { match in
print("Matched \(helloStr[match.start..<match.end])")
}
Of course this is a scratch implementation I made but it is to open discussion
on the topic. I feel the Regex struct itself will need more methods and
variables such as for flags and number of groups. Please provide feedback with
improvements to the code, concerns on the topic, or just open up discussion.
Thank you!
Joshua Alvarado
[email protected]
_______________________________________________
swift-evolution mailing list
[email protected]
https://lists.swift.org/mailman/listinfo/swift-evolution
