Add takeLast method for String, lists and arrays.

Check the parameter n in drop, take and takeLast methods.

libraries/tools/kotlin-stdlib-gen/src/templates/Filtering.kt

@@ -6,10 +6,12 @@ fun filtering(): List<GenericFunction> {
     val templates = arrayListOf<GenericFunction>()
 
     templates add f("drop(n: Int)") {
+        val n = "\$n"
         doc { "Returns a list containing all elements except first [n] elements" }
         returns("List<T>")
         body {
             """
+            require(n >= 0, { "Requested element count $n is less than zero." })
             var count = 0
             val list = ArrayList<T>()
             for (item in this) {
@@ -23,6 +25,7 @@ fun filtering(): List<GenericFunction> {
         returns(Sequences) { "Sequence<T>" }
         body(Sequences) {
             """
+            require(n >= 0, { "Requested element count $n is less than zero." })
             return DropSequence(this, n)
             """
         }
@@ -31,8 +34,9 @@ fun filtering(): List<GenericFunction> {
         body(Strings) { "return substring(Math.min(n, length()))" }
         returns(Strings) { "String" }
 
-        body(Collections, ArraysOfObjects, ArraysOfPrimitives) {
+        body(Collections) {
             """
+            require(n >= 0, { "Requested element count $n is less than zero." })
             if (n >= size())
                 return emptyList()
 
@@ -44,13 +48,29 @@ fun filtering(): List<GenericFunction> {
             return list
             """
         }
+
+        body(Lists, ArraysOfObjects, ArraysOfPrimitives) {
+            """
+            require(n >= 0, { "Requested element count $n is less than zero." })
+            if (n >= size())
+                return emptyList()
+
+            val list = ArrayList<T>(size() - n)
+            for (index in n..size() - 1) {
+                list.add(this[index])
+            }
+            return list
+            """
+        }
     }
 
     templates add f("take(n: Int)") {
+        val n = "\$n"
         doc { "Returns a list containing first [n] elements" }
         returns("List<T>")
         body {
             """
+            require(n >= 0, { "Requested element count $n is less than zero." })
             var count = 0
             val list = ArrayList<T>(n)
             for (item in this) {
@@ -70,6 +90,7 @@ fun filtering(): List<GenericFunction> {
         returns(Sequences) { "Sequence<T>" }
         body(Sequences) {
             """
+            require(n >= 0, { "Requested element count $n is less than zero." })
             return TakeSequence(this, n)
             """
         }
@@ -77,6 +98,7 @@ fun filtering(): List<GenericFunction> {
         include(Collections)
         body(Collections, ArraysOfObjects, ArraysOfPrimitives) {
             """
+            require(n >= 0, "Requested element count $n is less than zero.")
             var count = 0
             val realN = if (n > size()) size() else n
             val list = ArrayList<T>(realN)
@@ -90,6 +112,29 @@ fun filtering(): List<GenericFunction> {
         }
     }
 
+    templates add f("takeLast(n: Int)") {
+        val n = "\$n"
+        doc { "Returns a list containing last [n] elements" }
+        only(Lists, ArraysOfObjects, ArraysOfPrimitives, Strings)
+        returns("List<T>")
+
+        doc(Strings) { "Returns a string containing the last [n] characters from this string, or the entire string if this string is shorter"}
+        body(Strings) { "return substring(length() - Math.min(n, length()), length())" }
+        returns(Strings) { "String" }
+
+        body(Lists, ArraysOfObjects, ArraysOfPrimitives) {
+            """
+            require(n >= 0, { "Requested element count $n is less than zero." })
+            val size = size()
+            val realN = if (n > size) size else n
+            val list = ArrayList<T>(realN)
+            for (index in size - realN .. size - 1)
+                list.add(this[index])
+            return list
+            """
+        }
+    }
+
     templates add f("dropWhile(predicate: (T) -> Boolean)") {
         inline(true)