Adds -=, /=, and *= operation to Strings in Swift.

StringOps.swift

func -= ( left: inout String, right: String) -> String {
    let index = left.index(left.endIndex, offsetBy: -right.characters.count)
    return left.substring(to: index)
}


func *= ( left: inout String, right: String) -> String {
    
    var finalString = left
    
    for _ in 0..<right.characters.count {
        finalString.append(right)
    }
    
    return finalString
}

func /= ( left: inout String, right: String) -> String {
    let count1 = Double(left.characters.count) / Double(right.characters.count)
    let index = left.index(left.startIndex, offsetBy: Int(round(count1)))
    return left.substring(to: index)
}


// Results!

var hello = "Hello"
var goodbye = "by"

hello -= goodbye  // Hel
hello *= goodbye  // Hellobyby
hello /= goodbye  // Hel
hello += goodbye  // Helloby