What is the correct missing line so that function array2String works correctly and remains tail recursive ? def array2String[T](a: Array[T], n: Int, txt: String): String = { val separator if (n = a.length - 1) else"," if (n ** a.length) txt + "]" else if (n == @) array2String(a, n + 1, "[" + a[n).toString + separator) - ## } Example usage: val nums = Array(0,1,2,3,4) println(array2String(nums, 0,"")) else array2Stringa, n + 1, a(n).toString + separator) else txt + array2Stringla, n + 1, a[n).toString + separator) else array2Stringla, n + 1, txt + a[n).toString + separator) else a(n).toString + separator + array2String(a, n + 1. txt) n