June 2018 Update

Task/Optional-parameters/Kotlin/optional-parameters.kotlin

@@ -0,0 +1,46 @@
+// version 1.1.51
+
+typealias Table = List<List<String>>
+
+/* Note that if ordering is specified, first two parameters are ignored */
+fun Table.sort(
+    column: Int = 0,
+    reverse: Boolean = false,
+    ordering: Comparator<List<String>> =
+        if (!reverse) compareBy  { it[column] }
+        else compareByDescending { it[column] }
+) = this.sortedWith(ordering)
+
+fun Table.print(title: String) {
+    println(title)
+    for (i in 0 until this.size) {
+        for (j in 0 until this[0].size) System.out.print("%-3s  ".format(this[i][j]))
+        println()
+    }
+    println()
+}
+
+fun main(args: Array<String>) {
+    val table = listOf(
+        listOf("a", "b", "c"),
+        listOf("", "q", "z"),
+        listOf("zap", "zip", "Zot")
+    )
+    table.print("Original:")
+
+    val titles = listOf(
+        "Sorted by col 0:", "Sorted by col 1:", "Sorted by col 2:",
+        "Reverse sorted by col 0:", "Reverse sorted by col 1:", "Reverse Sorted by col 2"
+    )
+    val params = listOf(
+        0 to false, 1 to false, 2 to false, 0 to true, 1 to true, 2 to true
+    )
+    for ((i, title) in titles.withIndex()) {
+        val table2 = table.sort(params[i].first, params[i].second)
+        table2.print(title)
+    }
+    // using non-default Comparator (case insensitive by col 2, reversed)
+    val comp: Comparator<List<String>> = compareByDescending { it[2].toLowerCase() }
+    val table3 = table.sort(ordering = comp)
+    table3.print("Reverse case insensitive sort by col 2:")
+}