Add =~ operator for regex check

[fredpi]

I suggest to add a new infix operator =~ for checking whether a string matches a regex using the following implementation:

infix operator =~
func =~ (lhs: String, rhs: String) -> Bool {
    return lhs.range(of: rhs, options: .regularExpression) == lhs.range(of: lhs)
}

Use:

let stringMatchesRegex = "ABC" =~ "[A-Z]+"

[Jeehut]

I must say, the usage example looks really weird to me. If not documented that way, I'm not against adding such an operator. It's used in many other languages, so I think having an operator here is fine.

Note though, that I would also find it interesting to add support for getting captures easily. Until now I always used https://github.com/sharplet/Regex which I think both reads great and is a breeze to write.

[Jeehut]

Would you be up for a PR?

[fredpi]

Why's the usage example weird? Not such a common use, but very basic ;)

Captures would require more than just adding a single operator, so I would suggest only adding the operator for the initial PR, alright?

[Jeehut]

It's weird because it reads like this for an unexperienced developer:
"let stringMatchesRegex equal "ABC" equal (again?) "[A-~]+" ... WTF?" 😄

So for documentation, please use a more common usage example like this:

if "ABC" =~ "[A-Z]+" {
    // do something
}

One thing I wonder is, will Xcode give you Regex errors if you use the infix operator? I don't think so. Having used sharplet/Regex I know that it's working there which adds a lot of safety to defining Regex strings. Do you think, you can use an implementation that fixes that?

Regarding letting go of the captures: Sure, let's start with one feature and add others later on. What I was trying to say is: Wouldn't it go against one of the major three goals of Swift – namely being Expressive – to use an operator? Shouldn't we be using something like sharplet/Regex does, a type for the regular expression with lots of handy features?

I'm not entirely against this, but I'm not completely convinced it's a good addition either.

[fredpi]

You're probably right about the operator not really fitting into the Swift language. There's a reason operators such as ++ where removed.

With this in mind, I would actually withdraw my proposal, but suggest adding some other way for better regex processing to HandySwift.

[Jeehut]

What do you think about copying the classes Regex, MatchResult and String+ReplaceMatching off from sharplet/Regex and cleaning them up to only include the core functionality? I feel like it's pretty Swifty and has a good coverage of use cases.

[fredpi]

Seems like a good idea to include core regex functionality without blowing up this repo with too much regex interfaces. Will figure out what's needed imo and make a PR in the upcoming weeks.