[Swift] Expressively matching a Value againts a Sequence

doc.md

Usage:

let string = "one"

// using the global function
if string == any(of: "one", "two", "three") {
    // ..
}

// using the Equatable's extension function
if string.isAny(of: "one", "two", "three") {
    // ..
}

Equatable.swift

public extension Equatable {
    func isAny(of candidates: Self...) -> Bool {
        return candidates.contains(self)
    }
}

EquatableValueSequence.swift

public struct EquatableValueSequence<Value: Equatable> {
    private let values: [Value]
    
    public init(values: [Value]) {
        self.values = values
    }
    
    public static func ==(lhs: EquatableValueSequence<Value>, rhs: Value) -> Bool {
        return lhs.values.contains(rhs)
    }
    
    public static func ==(lhs: Value, rhs: EquatableValueSequence<Value>) -> Bool {
        return rhs == lhs
    }
}

Functions.swift

public func any<Value: Equatable>(of values: Value...) -> EquatableValueSequence<Value> {
    return EquatableValueSequence(values: values)
}