lesson 3 update

src/main/kotlin/lesson3/idiom16.kt

@@ -6,6 +6,8 @@ object AClass{
     val c = "c"
 }
 
+fun getAClass(): AClass? = null
+
 /**
  * [with]/[run]/[let] are used to create a scope with given argument or receiver
  */
@@ -14,20 +16,20 @@ fun main() {
     println("a = ${AClass.a}, b= ${AClass.b}, c = ${AClass.c}")
 
     // Using `with`
-    with(AClass){
+    val res = with(AClass){
         // AClass type is the receiver in this scope
-        println("a = $a, b= $b, c = $c")
+        println("a = $a, b = $b, c = $c")
         return@with "some value"
     }
 
     //using `run`
-    AClass.run {
+    getAClass()?.run {
         // the same as above
         println("a = $a, b= $b, c = $c")
     }
 
     //Using `let` to compose result. Not recommended to use without a need
-    val letResult = AClass.let {
+    val letResult = getAClass()?.let { arg ->
-        it.c + it.a
+        arg.c + arg.a
     }
 }

src/main/kotlin/lesson3/idiom17.kt

@@ -17,6 +17,8 @@ fun main() {
      */
     fun getAndIncrement() = i.also { i += 1 }
 
+    println(getAndIncrement())
+
     /**
      * Configure properties of an object (apply)
      * https://kotlinlang.org/docs/idioms.html#configure-properties-of-an-object-apply

src/main/kotlin/lesson3/idiom18-19.kt

@@ -29,9 +29,12 @@ fun main() {
 
     val newList = list + "f" + mutableList
 
+    println(newList)
+
     //Bonus
 
     val lambdaList = List(3){it.toString()}
+    println(lambdaList)
 }
 
 /**

src/main/kotlin/lesson3/idiom20-21.kt

@@ -15,5 +15,11 @@ fun main() {
         println("$k -> $v")
     }
 
-    val (a,b) = Pair(1, 2)
+    map.forEach { (k, v) -> println("$k -> $v")}
+
+    val (a, b) = Pair(1, 2)
+
+    val coord = doubleArrayOf(0.0, 1.0, 2.0)
+
+    val (x,y,z) = coord
 }

src/main/kotlin/lesson3/idiom22.kt

@@ -7,5 +7,5 @@ class AClassWithList{
 
 fun main() {
     val obj = AClassWithList()
-
+    obj.list
 }

src/main/kotlin/lesson3/idiom25.kt

@@ -1,13 +1,17 @@
-@file:JvmName("Idiom26Kt")
-
 package lesson3
 
 import kotlin.math.PI
 import kotlin.math.sin
 
 fun main() {
-    fun integrate(from: Double = 0.0, to: Double = 1.0, step: Double = 0.01, function: (Double) -> Double): Double {
+    fun integrate(
+        from: Double = 0.0,
+        to: Double = 1.0,
+        step: Double = 0.01,
+        function: (Double) -> Double,
+    ): Double {
         require(to > from)
+        require(step > 0)
         var sum = 0.0
         var pos = from
         while (pos < to) {
@@ -17,7 +21,9 @@ fun main() {
         return sum
     }
 
-    integrate { x -> x * x + 2 * x + 1 }
+    integrate { x ->
+        x * x + 2 * x + 1
+    }
     integrate(0.0, PI) { sin(it) }
     integrate(0.0, PI, step = 0.02) { sin(it) }
 }