Kotlin Functions, advanced

snippet.kt

fun join(strings: Collection<String>, separator: String = " ", 
         prefix: String = "", postfix: String = "") : String
{
  val result = StringBuilder(prefix)
  for((index, element) in strings.withIndex()) {
    if(index > 0) result.append(separator)
    result.append(element)
  }
  result.append(postfix)
  return result.toString()
}

join(list)
join(list, separator = ",")
join(list, prefix = "(", postfix = ")")