m

settings.gradle.kts

@@ -0,0 +1,5 @@
+pluginManagement {
+    val kotlinVersion: String by settings
+}
+
+rootProject.name = "kotlin-wheels"

src/commonMain/kotlin/ru/spbstu/wheels/Heap.kt

@@ -107,10 +107,13 @@ class BinaryHeap<T>(override val comparator: Comparator<T>): Heap<T>, AbstractMu
 
     /* Queue implementation */
     override fun put(value: T) { add(value) }
-    override fun take(): T = current?.also { removeAt(0) } ?: throw IllegalArgumentException("Heap is empty")
+    override fun take(): T {
+        require(size != 0) { "Heap is empty" }
+        return uncheckedCast(data[0].also { removeAt(0) })
+    }
     @Suppress(Warnings.UNCHECKED_CAST)
     override val current: T?
-        get() = data[0]
+        get() = runIf(size != 0) { data[0] }
 
     override fun isEmpty(): Boolean = size == 0
 }

src/commonMain/kotlin/ru/spbstu/wheels/Misc.kt

@@ -2,9 +2,18 @@
 package ru.spbstu.wheels
 
 import kotlin.contracts.ExperimentalContracts
+import kotlin.contracts.InvocationKind
 import kotlin.contracts.contract
 
 inline infix fun Int.times(body: (Int) -> Unit) {
     contract { callsInPlace(body) }
     repeat(this, body)
 }
+
+inline fun <T> runIf(condition: Boolean, body: () -> T): T? {
+    contract {
+        returnsNotNull() implies condition
+        callsInPlace(body, InvocationKind.AT_MOST_ONCE)
+    }
+    return if (condition) body() else null
+}

src/commonTest/kotlin/ru/spbstu/wheels/HeapTest.kt

@@ -3,9 +3,16 @@ package ru.spbstu.wheels
 import kotlin.test.Test
 import kotlin.random.Random
 import kotlin.test.assertEquals
+import kotlin.test.assertTrue
 
 class HeapTest {
 
+    @Test
+    fun emptyHeapTest() {
+        val h = heap<Int>()
+        assertEquals(null, h.current)
+    }
+
     @Test
     fun heapSortTest() {
 

src/commonTest/kotlin/ru/spbstu/wheels/MiscTest.kt

@@ -0,0 +1,25 @@
+package ru.spbstu.wheels
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class MiscTest {
+    @Test
+    fun repeat() {
+        var i = 0
+        3 times {
+            ++i
+        }
+        assertEquals(3, i)
+    }
+
+    @Test
+    fun makeIf() {
+        val numbers = 1..80
+
+        assertEquals(
+            (3..80 step 3).toList(),
+            numbers.mapNotNull { runIf(it % 3 == 0) { it } }
+        )
+    }
+}