From 14719728ddbe8b71379c7702d3985f1c8b352e15 Mon Sep 17 00:00:00 2001
From: Zohar Jackson <Jakobovski@users.noreply.github.com>
Date: Mon, 10 Sep 2018 11:44:00 -0400
Subject: Update kotlin.html.markdown

---
 kotlin.html.markdown | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'kotlin.html.markdown')

diff --git a/kotlin.html.markdown b/kotlin.html.markdown
index 0c787d7e..86d1baa0 100644
--- a/kotlin.html.markdown
+++ b/kotlin.html.markdown
@@ -370,6 +370,12 @@ fun useObject() {
     val someRef: Any = ObjectExample // we use objects name just as is
 }
 
+
+/* The not-null assertion operator (!!) converts any value to a non-null type and
+throws an exception if the value is null.
+*/
+var b: String? = "abc"
+val l = b!!.length
 ```
 
 ### Further Reading
-- 
cgit v1.2.3


From 9438e56ae90755582be35b6756e5b97dd5d1334a Mon Sep 17 00:00:00 2001
From: Muhammad Rifqi Fatchurrahman <muh_rif@live.com>
Date: Wed, 3 Oct 2018 00:56:58 +0700
Subject: [Kotlin/en] add kotlin operator overloading

---
 kotlin.html.markdown | 73 +++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 70 insertions(+), 3 deletions(-)

(limited to 'kotlin.html.markdown')

diff --git a/kotlin.html.markdown b/kotlin.html.markdown
index 86d1baa0..6ff7c1dc 100644
--- a/kotlin.html.markdown
+++ b/kotlin.html.markdown
@@ -65,7 +65,7 @@ fun helloWorld(val name : String) {
     A template expression starts with a dollar sign ($).
     */
     val fooTemplateString = "$fooString has ${fooString.length} characters"
-    println(fooTemplateString) // => My String Is Here! has 18 characters 
+    println(fooTemplateString) // => My String Is Here! has 18 characters
 
     /*
     For a variable to hold null it must be explicitly specified as nullable.
@@ -175,12 +175,12 @@ fun helloWorld(val name : String) {
     // Objects can be destructured into multiple variables.
     val (a, b, c) = fooCopy
     println("$a $b $c") // => 1 100 4
-    
+
     // destructuring in "for" loop
     for ((a, b, c) in listOf(fooData)) {
         println("$a $b $c") // => 1 100 4
     }
-    
+
     val mapData = mapOf("a" to 1, "b" to 2)
     // Map.Entry is destructurable as well
     for ((key, value) in mapData) {
@@ -347,6 +347,8 @@ fun helloWorld(val name : String) {
 
     println(EnumExample.A) // => A
     println(ObjectExample.hello()) // => hello
+
+    testOperator()
 }
 
 // Enum classes are similar to Java enum types.
@@ -376,6 +378,71 @@ throws an exception if the value is null.
 */
 var b: String? = "abc"
 val l = b!!.length
+
+/* You can add many custom operations using symbol like +, to particular instance
+by overloading the built-in kotlin operator, using "operator" keyword
+
+below is the sample class to add some operator, and the most basic example
+*/
+data class SomeClass(var savedValue: Int = 0)
+
+// instance += valueToAdd
+operator fun SomeClass.plusAssign(valueToAdd: Int) {
+  this.savedValue += valueToAdd  
+}
+
+// -instance
+operator fun SomeClass.unaryMinus() = SomeClass(-this.savedValue)
+
+// ++instance or instance++
+operator fun SomeClass.inc() = SomeClass(this.savedValue + 1)
+
+// instance * other
+operator fun SomeClass.times(other: SomeClass) =
+  SomeClass(this.savedValue * other.savedValue)
+
+// an overload for multiply
+operator fun SomeClass.times(value: Int) = SomeClass(this.savedValue * value)
+
+// other in instance
+operator fun SomeClass.contains(other: SomeClass) =
+  other.savedValue == this.savedValue
+
+// instance[dummyIndex] = valueToSet
+operator fun SomeClass.set(dummyIndex: Int, valueToSet: Int) {
+  this.savedValue = valueToSet + dummyIndex
+}
+
+// instance()
+operator fun SomeClass.invoke() {
+  println("instance invoked by invoker")
+}
+
+/* return type must be Integer,
+so that, it can be translated to "returned value" compareTo 0
+
+for equality (==,!=) using operator will violates overloading equals function,
+since it is already defined in Any class
+*/
+operator fun SomeClass.compareTo(other: SomeClass) =
+  this.savedValue - other.savedValue
+
+fun testOperator() {
+  var x = SomeClass(4)
+
+  println(x) // => "SomeClass(savedValue=4)"
+  x += 10
+  println(x) // => "SomeClass(savedValue=14)"
+  println(-x) // => "SomeClass(savedValue=-14)"
+  println(++x) // => "SomeClass(savedValue=15)"
+  println(x * SomeClass(3)) // => "SomeClass(savedValue=45)"
+  println(x * 2) // => "SomeClass(savedValue=30)"
+  println(SomeClass(15) in x) // => true
+  x[2] = 10
+  println(x) // => "SomeClass(savedValue=12)"
+  x() // => "instance invoked by invoker"
+  println(x >= 15) // => false
+}
 ```
 
 ### Further Reading
-- 
cgit v1.2.3