createStack.swift

func createStack<T>(with array:[T] = [], divider: (top: String, bottom: String) = (top:"-", bottom:"+")) -> _Stack<T> {
    var array:[T] = array
    var typeDescription: String { String(describing:T.self) }
    var topDivider     : String {
        array.count > 0
        ? "\(3*divider.top) " +       "Stack<\(typeDescription)>: \(array.count) elements " + "\(3*divider.top)" + "\n"
        : "\(3*divider.top) " + "Empty Stack<\(typeDescription)> "                          + "\(3*divider.top)" + "\n"
    }
    var bottomDivider  : String { divider.bottom * max((topDivider.count - 1), 0) + "\n" }
    return (
          push: { array.append($0)                                                                               },
           pop: { array.count > 0 ? array.remove(at:array.count - 1) : nil                                       },
          peek: { array.last                                                                                     },
        string: { topDivider + array.reversed().reduce("") { $0 + String(reflecting:$1) + "\n" } + bottomDivider }
    )
}