More of stdlib. (#183)

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/descriptors/utils.kt

@@ -37,5 +37,5 @@ val PropertyDescriptor.backingField: PropertyDescriptor?
     }
 
 fun DeclarationDescriptor.deepPrint() {
-    this!!.accept(DeepPrintVisitor(PrintVisitor()), 0)
+    this.accept(DeepPrintVisitor(PrintVisitor()), 0)
 }

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/IrToBitcode.kt

@@ -1334,6 +1334,8 @@ internal class CodeGeneratorVisitor(val context: Context) : IrElementVisitorVoid
 
     private fun genInstanceOf(obj: LLVMValueRef, type: KotlinType): LLVMValueRef {
         val dstDescriptor = TypeUtils.getClassDescriptor(type)                         // Get class descriptor for dst type.
+        // Reified parameters are not yet supported.
+        assert(dstDescriptor != null)
         val dstTypeInfo   = codegen.typeInfoValue(dstDescriptor!!)                     // Get TypeInfo for dst type.
         val srcObjInfoPtr = codegen.bitcast(codegen.kObjHeaderPtr, obj)                // Cast src to ObjInfoPtr.
         val args          = listOf(srcObjInfoPtr, dstTypeInfo)                         // Create arg list.

runtime/src/main/cpp/Operator.cpp

@@ -370,7 +370,11 @@ KInt   Kotlin_Float_bits              (KFloat a) {
   return alias.i;
 }
 
-//--- Double ------------------------------------------------------------------//
+KBoolean Kotlin_Float_isNaN           (KFloat a)          { return isnan(a); }
+KBoolean Kotlin_Float_isInfinite      (KFloat a)          { return isinf(a); }
+KBoolean Kotlin_Float_isFinite        (KFloat a)          { return isfinite(a); }
+
+  //--- Double ------------------------------------------------------------------//
 
 KInt    Kotlin_Double_compareTo_Byte   (KDouble a, KByte   b) { if (a == b) return 0; return (a < b) ? -1 : 1; }
 KInt    Kotlin_Double_compareTo_Short  (KDouble a, KShort  b) { if (a == b) return 0; return (a < b) ? -1 : 1; }
@@ -435,4 +439,8 @@ KLong   Kotlin_Double_bits             (KDouble a) {
   return alias.l;
 }
 
+KBoolean Kotlin_Double_isNaN           (KDouble a)          { return isnan(a); }
+KBoolean Kotlin_Double_isInfinite      (KDouble a)          { return isinf(a); }
+KBoolean Kotlin_Double_isFinite        (KDouble a)          { return isfinite(a); }
+
 }  // extern "C"

runtime/src/main/kotlin/konan/Annotations.kt

@@ -31,6 +31,31 @@ public annotation class Used
  */
 public annotation class FixmeInner
 
+/**
+ * Need to be fixed because of reification support.
+ */
+public annotation class FixmeReified
+
+/**
+ * Need to be fixed because of sorting support.
+ */
+public annotation class FixmeSorting
+
+/**
+ * Need to be fixed because of specialization support.
+ */
+public annotation class FixmeSpecialization
+
+/**
+ * Need to be fixed because of sequences support.
+ */
+public annotation class FixmeSequences
+
+/**
+ * Need to be fixed because of variance support.
+ */
+public annotation class FixmeVariance
+
 /**
  * Need to be fixed.
  */

runtime/src/main/kotlin/kotlin/Annotations.kt

@@ -6,7 +6,8 @@ package kotlin
  */
 //@Target(CLASS, ANNOTATION_CLASS, PROPERTY, FIELD, LOCAL_VARIABLE, VALUE_PARAMETER,
 //        CONSTRUCTOR, FUNCTION, PROPERTY_GETTER, PROPERTY_SETTER, TYPE, EXPRESSION, FILE, TYPEALIAS)
-@Target(AnnotationTarget.TYPE, AnnotationTarget.VALUE_PARAMETER, AnnotationTarget.EXPRESSION)
+@Target(AnnotationTarget.TYPE, AnnotationTarget.VALUE_PARAMETER, AnnotationTarget.EXPRESSION,
+        AnnotationTarget.LOCAL_VARIABLE, AnnotationTarget.FUNCTION)
 //@Retention(SOURCE)
 public annotation class Suppress(vararg val names: String)
 

runtime/src/main/kotlin/kotlin/Array.kt

@@ -48,13 +48,6 @@ private class IteratorImpl<T>(val collection: Array<T>) : Iterator<T> {
 
 fun <T> arrayOf(vararg elements: T) : Array<out T> = elements
 
-public fun <T, C : MutableCollection<in T>> Array<out T>.toCollection(destination: C): C {
-    for (item in this) {
-        destination.add(item)
-    }
-    return destination
-}
-
 @kotlin.internal.InlineOnly
 public inline operator fun <T> Array<T>.plus(elements: Array<T>): Array<T> {
     val result = copyOfUninitializedElements(this.size + elements.size)

runtime/src/main/kotlin/kotlin/Arrays.kt

@@ -488,14 +488,6 @@ public inline fun <T> Array<out T>.lastOrNull(predicate: (T) -> Boolean): T? {
     return null
 }
 
-/**
- * Returns `true` if the array is empty.
- */
-@kotlin.internal.InlineOnly
-public inline fun <T> Array<out T>.isEmpty(): Boolean {
-    return size == 0
-}
-
 /**
  * Returns the range of valid indices for the array.
  */
@@ -592,4 +584,300 @@ public fun Array<out Double>.sum(): Double {
     return sum
 }
 
+// From _Arrays.kt.
 
+/**
+ * Returns `true` if the array is empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T> Array<out T>.isEmpty(): Boolean {
+    return size == 0
+}
+
+/**
+ * Returns `true` if the array is empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun ByteArray.isEmpty(): Boolean {
+    return size == 0
+}
+
+/**
+ * Returns `true` if the array is empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun ShortArray.isEmpty(): Boolean {
+    return size == 0
+}
+
+/**
+ * Returns `true` if the array is empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun IntArray.isEmpty(): Boolean {
+    return size == 0
+}
+
+/**
+ * Returns `true` if the array is empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun LongArray.isEmpty(): Boolean {
+    return size == 0
+}
+
+/**
+ * Returns `true` if the array is empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun FloatArray.isEmpty(): Boolean {
+    return size == 0
+}
+
+/**
+ * Returns `true` if the array is empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun DoubleArray.isEmpty(): Boolean {
+    return size == 0
+}
+/**
+ * Returns `true` if the array is empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun BooleanArray.isEmpty(): Boolean {
+    return size == 0
+}
+
+/**
+ * Returns `true` if the array is empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun CharArray.isEmpty(): Boolean {
+    return size == 0
+}
+
+/**
+ * Returns `true` if the array is not empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T> Array<out T>.isNotEmpty(): Boolean {
+    return !isEmpty()
+}
+
+/**
+ * Returns `true` if the array is not empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun ByteArray.isNotEmpty(): Boolean {
+    return !isEmpty()
+}
+
+/**
+ * Returns `true` if the array is not empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun ShortArray.isNotEmpty(): Boolean {
+    return !isEmpty()
+}
+
+/**
+ * Returns `true` if the array is not empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun IntArray.isNotEmpty(): Boolean {
+    return !isEmpty()
+}
+
+/**
+ * Returns `true` if the array is not empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun LongArray.isNotEmpty(): Boolean {
+    return !isEmpty()
+}
+
+/**
+ * Returns `true` if the array is not empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun FloatArray.isNotEmpty(): Boolean {
+    return !isEmpty()
+}
+
+/**
+ * Returns `true` if the array is not empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun DoubleArray.isNotEmpty(): Boolean {
+    return !isEmpty()
+}
+
+/**
+ * Returns `true` if the array is not empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun BooleanArray.isNotEmpty(): Boolean {
+    return !isEmpty()
+}
+
+/**
+ * Returns `true` if the array is not empty.
+ */
+@kotlin.internal.InlineOnly
+public inline fun CharArray.isNotEmpty(): Boolean {
+    return !isEmpty()
+}
+
+/**
+ * Appends all elements to the given [destination] collection.
+ */
+public fun <T, C : MutableCollection<in T>> Array<out T>.toCollection(destination: C): C {
+    for (item in this) {
+        destination.add(item)
+    }
+    return destination
+}
+
+/**
+ * Appends all elements to the given [destination] collection.
+ */
+public fun <C : MutableCollection<in Byte>> ByteArray.toCollection(destination: C): C {
+    for (item in this) {
+        destination.add(item)
+    }
+    return destination
+}
+
+/**
+ * Appends all elements to the given [destination] collection.
+ */
+public fun <C : MutableCollection<in Short>> ShortArray.toCollection(destination: C): C {
+    for (item in this) {
+        destination.add(item)
+    }
+    return destination
+}
+
+/**
+ * Appends all elements to the given [destination] collection.
+ */
+public fun <C : MutableCollection<in Int>> IntArray.toCollection(destination: C): C {
+    for (item in this) {
+        destination.add(item)
+    }
+    return destination
+}
+
+/**
+ * Appends all elements to the given [destination] collection.
+ */
+public fun <C : MutableCollection<in Long>> LongArray.toCollection(destination: C): C {
+    for (item in this) {
+        destination.add(item)
+    }
+    return destination
+}
+
+/**
+ * Appends all elements to the given [destination] collection.
+ */
+public fun <C : MutableCollection<in Float>> FloatArray.toCollection(destination: C): C {
+    for (item in this) {
+        destination.add(item)
+    }
+    return destination
+}
+
+/**
+ * Appends all elements to the given [destination] collection.
+ */
+public fun <C : MutableCollection<in Double>> DoubleArray.toCollection(destination: C): C {
+    for (item in this) {
+        destination.add(item)
+    }
+    return destination
+}
+
+/**
+ * Appends all elements to the given [destination] collection.
+ */
+public fun <C : MutableCollection<in Boolean>> BooleanArray.toCollection(destination: C): C {
+    for (item in this) {
+        destination.add(item)
+    }
+    return destination
+}
+
+/**
+ * Appends all elements to the given [destination] collection.
+ */
+public fun <C : MutableCollection<in Char>> CharArray.toCollection(destination: C): C {
+    for (item in this) {
+        destination.add(item)
+    }
+    return destination
+}
+
+/**
+ * Returns a [HashSet] of all elements.
+ */
+public fun <T> Array<out T>.toHashSet(): HashSet<T> {
+    return toCollection(HashSet<T>(mapCapacity(size)))
+}
+
+/**
+ * Returns a [HashSet] of all elements.
+ */
+public fun ByteArray.toHashSet(): HashSet<Byte> {
+    return toCollection(HashSet<Byte>(mapCapacity(size)))
+}
+
+/**
+ * Returns a [HashSet] of all elements.
+ */
+public fun ShortArray.toHashSet(): HashSet<Short> {
+    return toCollection(HashSet<Short>(mapCapacity(size)))
+}
+
+/**
+ * Returns a [HashSet] of all elements.
+ */
+public fun IntArray.toHashSet(): HashSet<Int> {
+    return toCollection(HashSet<Int>(mapCapacity(size)))
+}
+
+/**
+ * Returns a [HashSet] of all elements.
+ */
+public fun LongArray.toHashSet(): HashSet<Long> {
+    return toCollection(HashSet<Long>(mapCapacity(size)))
+}
+
+/**
+ * Returns a [HashSet] of all elements.
+ */
+public fun FloatArray.toHashSet(): HashSet<Float> {
+    return toCollection(HashSet<Float>(mapCapacity(size)))
+}
+
+/**
+ * Returns a [HashSet] of all elements.
+ */
+public fun DoubleArray.toHashSet(): HashSet<Double> {
+    return toCollection(HashSet<Double>(mapCapacity(size)))
+}
+
+/**
+ * Returns a [HashSet] of all elements.
+ */
+public fun BooleanArray.toHashSet(): HashSet<Boolean> {
+    return toCollection(HashSet<Boolean>(mapCapacity(size)))
+}
+
+/**
+ * Returns a [HashSet] of all elements.
+ */
+public fun CharArray.toHashSet(): HashSet<Char> {
+    return toCollection(HashSet<Char>(mapCapacity(size)))
+}

runtime/src/main/kotlin/kotlin/Comparable.kt

@@ -1,5 +1,7 @@
 package kotlin
 
+import kotlin.comparisons.Comparator
+
 /**
  * Classes which inherit from this interface have a defined total ordering between their instances.
  */
@@ -11,3 +13,6 @@ public interface Comparable<in T> {
      */
     public operator fun compareTo(other: T): Int
 }
+
+typealias Comparator<T> = kotlin.comparisons.Comparator<T>
+

runtime/src/main/kotlin/kotlin/Numbers.kt

@@ -0,0 +1,39 @@
+package kotlin
+
+/**
+ * Returns `true` if the specified number is a
+ * Not-a-Number (NaN) value, `false` otherwise.
+ */
+@SymbolName("Kotlin_Double_isNaN")
+external public fun Double.isNaN(): Boolean
+
+/**
+ * Returns `true` if the specified number is a
+ * Not-a-Number (NaN) value, `false` otherwise.
+ */
+@SymbolName("Kotlin_Float_isNaN")
+external public fun Float.isNaN(): Boolean
+
+/**
+ * Returns `true` if this value is infinitely large in magnitude.
+ */
+@SymbolName("Kotlin_Double_isInfinite")
+external public fun Double.isInfinite(): Boolean
+
+/**
+ * Returns `true` if this value is infinitely large in magnitude.
+ */
+@SymbolName("Kotlin_Float_isInfinite")
+external public fun Float.isInfinite(): Boolean
+
+/**
+ * Returns `true` if the argument is a finite floating-point value; returns `false` otherwise (for `NaN` and infinity arguments).
+ */
+@SymbolName("Kotlin_Double_isFinite")
+external public fun Double.isFinite(): Boolean
+
+/**
+ * Returns `true` if the argument is a finite floating-point value; returns `false` otherwise (for `NaN` and infinity arguments).
+ */
+@SymbolName("Kotlin_Float_isFinite")
+external public fun Float.isFinite(): Boolean

runtime/src/main/kotlin/kotlin/collections/ArrayList.kt

@@ -5,7 +5,7 @@ class ArrayList<E> private constructor(
         private var offset: Int,
         private var length: Int,
         private val backing: ArrayList<E>?
-) : MutableList<E> {
+) : MutableList<E>, RandomAccess {
 
     constructor() : this(10)
 

runtime/src/main/kotlin/kotlin/collections/HashMap.kt

@@ -670,4 +670,7 @@ internal class HashMapEntrySet<K, V> internal constructor(
         @Suppress("UNCHECKED_CAST") // todo: get rid of unchecked cast here somehow
         return size == other.size && backing.containsAllEntries(other as Collection<Map.Entry<*, *>>)
     }
-}
+}
+
+// This hash map keeps insertion order.
+typealias LinkedHashMap<K, V> = HashMap<K, V>

runtime/src/main/kotlin/kotlin/collections/HashSet.kt

@@ -82,4 +82,7 @@ class HashSet<K> internal constructor(
     // ---------------------------- private ----------------------------
 
     private fun contentEquals(other: Set<K>): Boolean = size == other.size && containsAll(other)
-}
+}
+
+// This hash set keeps insertion order.
+typealias LinkedHashSet<V> = HashSet<V>

runtime/src/main/kotlin/kotlin/collections/IndexedValue.kt

@@ -0,0 +1,9 @@
+package kotlin.collections
+
+/**
+ * Data class representing a value from a collection or sequence, along with its index in that collection or sequence.
+ *
+ * @property value the underlying value.
+ * @property index the index of the value in the collection or sequence.
+ */
+public data class IndexedValue<out T>(public val index: Int, public val value: T)

runtime/src/main/kotlin/kotlin/collections/Iterables.kt

@@ -0,0 +1,82 @@
+package kotlin.collections
+
+/**
+ * Given an [iterator] function constructs an [Iterable] instance that returns values through the [Iterator]
+ * provided by that function.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T> Iterable(crossinline iterator: () -> Iterator<T>): Iterable<T> = object : Iterable<T> {
+    override fun iterator(): Iterator<T> = iterator()
+}
+
+/**
+ * A wrapper over another [Iterable] (or any other object that can produce an [Iterator]) that returns
+ * an indexing iterator.
+ */
+internal class IndexingIterable<out T>(private val iteratorFactory: () -> Iterator<T>) : Iterable<IndexedValue<T>> {
+    override fun iterator(): Iterator<IndexedValue<T>> = IndexingIterator(iteratorFactory())
+}
+
+
+/**
+ * Returns the size of this iterable if it is known, or `null` otherwise.
+ */
+@PublishedApi
+internal fun <T> Iterable<T>.collectionSizeOrNull(): Int? = if (this is Collection<*>) this.size else null
+
+/**
+ * Returns the size of this iterable if it is known, or the specified [default] value otherwise.
+ */
+@PublishedApi
+internal fun <T> Iterable<T>.collectionSizeOrDefault(default: Int): Int = if (this is Collection<*>) this.size else default
+
+/** Returns true when it's safe to convert this collection to a set without changing contains method behavior. */
+private fun <T> Collection<T>.safeToConvertToSet() = size > 2 && this is ArrayList
+
+/** Converts this collection to a set, when it's worth so and it doesn't change contains method behavior. */
+internal fun <T> Iterable<T>.convertToSetForSetOperationWith(source: Iterable<T>): Collection<T> =
+        when(this) {
+            is Set -> this
+            is Collection ->
+                when {
+                    source is Collection && source.size < 2 -> this
+                    else -> if (this.safeToConvertToSet()) toHashSet() else this
+                }
+            else -> toHashSet()
+        }
+
+/** Converts this collection to a set, when it's worth so and it doesn't change contains method behavior. */
+internal fun <T> Iterable<T>.convertToSetForSetOperation(): Collection<T> =
+        when(this) {
+            is Set -> this
+            is Collection -> if (this.safeToConvertToSet()) toHashSet() else this
+            else -> toHashSet()
+        }
+
+
+/**
+ * Returns a single list of all elements from all collections in the given collection.
+ */
+public fun <T> Iterable<Iterable<T>>.flatten(): List<T> {
+    val result = ArrayList<T>()
+    for (element in this) {
+        result.addAll(element)
+    }
+    return result
+}
+
+/**
+ * Returns a pair of lists, where
+ * *first* list is built from the first values of each pair from this collection,
+ * *second* list is built from the second values of each pair from this collection.
+ */
+public fun <T, R> Iterable<Pair<T, R>>.unzip(): Pair<List<T>, List<R>> {
+    val expectedSize = collectionSizeOrDefault(10)
+    val listT = ArrayList<T>(expectedSize)
+    val listR = ArrayList<R>(expectedSize)
+    for (pair in this) {
+        listT.add(pair.first)
+        listR.add(pair.second)
+    }
+    return listT to listR
+}

runtime/src/main/kotlin/kotlin/collections/Iterators.kt

@@ -63,3 +63,31 @@ public abstract class BooleanIterator : Iterator<Boolean> {
     /** Returns the next value in the sequence without boxing. */
     public abstract fun nextBoolean(): Boolean
 }
+
+/**
+ * Returns the given iterator itself. This allows to use an instance of iterator in a `for` loop.
+ */
+@kotlin.internal.InlineOnly
+public inline operator fun <T> Iterator<T>.iterator(): Iterator<T> = this
+
+/**
+ * Returns an [Iterator] wrapping each value produced by this [Iterator] with the [IndexedValue],
+ * containing value and it's index.
+ */
+public fun <T> Iterator<T>.withIndex(): Iterator<IndexedValue<T>> = IndexingIterator(this)
+
+/**
+ * Performs the given [operation] on each element of this [Iterator].
+ */
+public inline fun <T> Iterator<T>.forEach(operation: (T) -> Unit) : Unit {
+    for (element in this) operation(element)
+}
+
+/**
+ * Iterator transforming original `iterator` into iterator of [IndexedValue], counting index from zero.
+ */
+internal class IndexingIterator<out T>(private val iterator: Iterator<T>) : Iterator<IndexedValue<T>> {
+    private var index = 0
+    final override fun hasNext(): Boolean = iterator.hasNext()
+    final override fun next(): IndexedValue<T> = IndexedValue(index++, iterator.next())
+}

runtime/src/main/kotlin/kotlin/collections/Maps.kt

@@ -97,8 +97,7 @@ internal fun mapCapacity(expectedSize: Int): Int {
     return Int.MAX_VALUE // any large value
 }
 
-@Fixme
-private const val INT_MAX_POWER_OF_TWO: Int = 0x40000000 // Int.MAX_VALUE / 2 + 1
+private const val INT_MAX_POWER_OF_TWO: Int = Int.MAX_VALUE / 2 + 1
 
 /** Returns `true` if this map is not empty. */
 @kotlin.internal.InlineOnly
@@ -192,19 +191,14 @@ public inline fun <K, V> Map.Entry<K, V>.toPair(): Pair<K, V> = Pair(key, value)
 public inline fun <K, V> Map<K, V>.getOrElse(key: K, defaultValue: () -> V): V = get(key) ?: defaultValue()
 
 
-@Fixme
 internal inline fun <K, V> Map<K, V>.getOrElseNullable(key: K, defaultValue: () -> V): V {
-    TODO()
+    val value = get(key)
+    if (value == null && !containsKey(key)) {
+        return defaultValue()
+    } else {
+        return value as V
+    }
 }
-//    val value = get(key)
-//    if (value == null && !containsKey(key)) {
-//        return defaultValue()
-//    } else {
-//        return value as V
-//    }
-//}
-
-
 
 /**
  * Returns the value for the given key. If the key is not found in the map, calls the [defaultValue] function,
@@ -242,11 +236,9 @@ public inline operator fun <K, V> MutableMap<K, V>.iterator(): MutableIterator<M
  * Populates the given [destination] map with entries having the keys of this map and the values obtained
  * by applying the [transform] function to each entry in this [Map].
  */
-@Fixme
 @kotlin.internal.InlineOnly
 public inline fun <K, V, R, M : MutableMap<in K, in R>> Map<out K, V>.mapValuesTo(destination: M, transform: (Map.Entry<K, V>) -> R): M {
-    TODO()
-//    return entries.associateByTo(destination, { it.key }, transform)
+    return entries.associateByTo(destination, { it.key }, transform)
 }
 
 /**
@@ -258,8 +250,7 @@ public inline fun <K, V, R, M : MutableMap<in K, in R>> Map<out K, V>.mapValuesT
  */
 @kotlin.internal.InlineOnly
 public inline fun <K, V, R, M : MutableMap<in R, in V>> Map<out K, V>.mapKeysTo(destination: M, transform: (Map.Entry<K, V>) -> R): M {
-    TODO()
-//    return entries.associateByTo(destination, transform, { it.value })
+    return entries.associateByTo(destination, transform, { it.value })
 }
 
 /**
@@ -297,9 +288,12 @@ public fun <K, V> MutableMap<in K, in V>.putAll(pairs: Sequence<Pair<K,V>>): Uni
  *
  * @sample samples.collections.Maps.Transforms.mapValues
  */
-//public inline fun <K, V, R> Map<out K, V>.mapValues(transform: (Map.Entry<K, V>) -> R): Map<K, R> {
-//    return mapValuesTo(HashMap<K, R>(mapCapacity(size)), transform) // .optimizeReadOnlyMap()
-//}
+public inline fun <K, V, R> Map<out K, V>.mapValues(transform: (Map.Entry<K, V>) -> R): Map<K, R> {
+    @Suppress("NON_PUBLIC_CALL_FROM_PUBLIC_INLINE")
+    return mapValuesTo(HashMap<K, R>(
+            mapCapacity(size)),
+            transform).optimizeReadOnlyMap()
+}
 
 /**
  * Returns a new Map with entries having the keys obtained by applying the [transform] function to each entry in this
@@ -312,9 +306,12 @@ public fun <K, V> MutableMap<in K, in V>.putAll(pairs: Sequence<Pair<K,V>>): Uni
  *
  * @sample samples.collections.Maps.Transforms.mapKeys
  */
-//public inline fun <K, V, R> Map<out K, V>.mapKeys(transform: (Map.Entry<K, V>) -> R): Map<R, V> {
-//    return mapKeysTo(HashMap<R, V>(mapCapacity(size)), transform) // .optimizeReadOnlyMap()
-//}
+public inline fun <K, V, R> Map<out K, V>.mapKeys(transform: (Map.Entry<K, V>) -> R): Map<R, V> {
+    @Suppress("NON_PUBLIC_CALL_FROM_PUBLIC_INLINE")
+    return mapKeysTo(HashMap<R, V>(
+            mapCapacity(size)),
+            transform).optimizeReadOnlyMap()
+}
 
 /**
  * Returns a map containing all key-value pairs with keys matching the given [predicate].
@@ -412,6 +409,7 @@ public fun <K, V> Iterable<Pair<K, V>>.toMap(): Map<K, V> {
 /**
  * Populates and returns the [destination] mutable map with key-value pairs from the given collection of pairs.
  */
+@Fixme
 public fun <K, V, M : MutableMap<in K, in V>> Iterable<Pair<K, V>>.toMap(destination: M): M {
     for (pair in this) {
         destination.put(pair.first, pair.second)
@@ -434,6 +432,7 @@ public fun <K, V> Array<out Pair<K, V>>.toMap(): Map<K, V> = when(size) {
 /**
  *  Populates and returns the [destination] mutable map with key-value pairs from the given array of pairs.
  */
+@Fixme
 public fun <K, V, M : MutableMap<in K, in V>> Array<out Pair<K, V>>.toMap(destination: M): M {
 //        = destination.apply { putAll(this@toMap) }
     for (pair in this) {
@@ -452,6 +451,7 @@ public fun <K, V> Sequence<Pair<K, V>>.toMap(): Map<K, V> = toMap(HashMap<K, V>(
 /**
  * Populates and returns the [destination] mutable map with key-value pairs from the given sequence of pairs.
  */
+@Fixme
 public fun <K, V, M : MutableMap<in K, in V>> Sequence<Pair<K, V>>.toMap(destination: M): M {
     for (pair in this) {
         destination.put(pair.first, pair.second)
@@ -484,15 +484,15 @@ public fun <K, V> Map</*out */K, V>.toMutableMap(): MutableMap<K, V> = HashMap(t
 public fun <K, V, M : MutableMap<in K, in V>> Map<out K, V>.toMap(destination: M): M
         = destination.apply { putAll(this@toMap) }
 
-// TODO: fix me, once have correct type variance in HashMap.
 /**
  * Creates a new read-only map by replacing or adding an entry to this map from a given key-value [pair].
  *
  * The returned map preserves the entry iteration order of the original map.
  * The [pair] is iterated in the end if it has a unique key.
  */
-// public operator fun <K, V> Map<out K, V>.plus(pair: Pair<K, V>): Map<K, V>
-//        = if (this.isEmpty()) mapOf(pair) else HashMap(this).apply { put(pair.first, pair.second) }
+@FixmeVariance
+public operator fun <K, V> Map</*out */K, V>.plus(pair: Pair<K, V>): Map<K, V>
+        = if (this.isEmpty()) mapOf(pair) else HashMap(this).apply { put(pair.first, pair.second) }
 
 /**
  * Creates a new read-only map by replacing or adding entries to this map from a given collection of key-value [pairs].
@@ -500,8 +500,9 @@ public fun <K, V, M : MutableMap<in K, in V>> Map<out K, V>.toMap(destination: M
  * The returned map preserves the entry iteration order of the original map.
  * Those [pairs] with unique keys are iterated in the end in the order of [pairs] collection.
  */
-//public operator fun <K, V> Map<out K, V>.plus(pairs: Iterable<Pair<K, V>>): Map<K, V>
-//        = if (this.isEmpty()) pairs.toMap() else HashMap(this).apply { putAll(pairs) }
+@FixmeVariance
+public operator fun <K, V> Map</*out */K, V>.plus(pairs: Iterable<Pair<K, V>>): Map<K, V>
+        = if (this.isEmpty()) pairs.toMap() else HashMap(this).apply { putAll(pairs) }
 
 /**
  * Creates a new read-only map by replacing or adding entries to this map from a given array of key-value [pairs].
@@ -509,8 +510,9 @@ public fun <K, V, M : MutableMap<in K, in V>> Map<out K, V>.toMap(destination: M
  * The returned map preserves the entry iteration order of the original map.
  * Those [pairs] with unique keys are iterated in the end in the order of [pairs] array.
  */
-//public operator fun <K, V> Map<out K, V>.plus(pairs: Array<out Pair<K, V>>): Map<K, V>
-//        = if (this.isEmpty()) pairs.toMap() else HashMap(this).apply { putAll(pairs) }
+@FixmeVariance
+public operator fun <K, V> Map</*out */K, V>.plus(pairs: Array<out Pair<K, V>>): Map<K, V>
+        = if (this.isEmpty()) pairs.toMap() else HashMap(this).apply { putAll(pairs) }
 
 /**
  * Creates a new read-only map by replacing or adding entries to this map from a given sequence of key-value [pairs].
@@ -518,8 +520,8 @@ public fun <K, V, M : MutableMap<in K, in V>> Map<out K, V>.toMap(destination: M
  * The returned map preserves the entry iteration order of the original map.
  * Those [pairs] with unique keys are iterated in the end in the order of [pairs] sequence.
  */
-//public operator fun <K, V> Map<out K, V>.plus(pairs: Sequence<Pair<K, V>>): Map<K, V>
-//        = HashMap(this).apply { putAll(pairs) }.optimizeReadOnlyMap()
+public operator fun <K, V> Map</*out */K, V>.plus(pairs: Sequence<Pair<K, V>>): Map<K, V>
+        = HashMap(this).apply { putAll(pairs) }.optimizeReadOnlyMap()
 
 /**
  * Creates a new read-only map by replacing or adding entries to this map from another [map].
@@ -527,8 +529,9 @@ public fun <K, V, M : MutableMap<in K, in V>> Map<out K, V>.toMap(destination: M
  * The returned map preserves the entry iteration order of the original map.
  * Those entries of another [map] that are missing in this map are iterated in the end in the order of that [map].
  */
-//public operator fun <K, V> Map<out K, V>.plus(map: Map<out K, V>): Map<K, V>
-//        = HashMap(this).apply { putAll(map) }
+@FixmeVariance
+public operator fun <K, V> Map</*out */K, V>.plus(map: Map</*out */K, V>): Map<K, V>
+        = HashMap(this).apply { putAll(map) }
 
 /**
  * Appends or replaces the given [pair] in this mutable map.

runtime/src/main/kotlin/kotlin/collections/MutableCollections.kt

@@ -1,5 +1,7 @@
 package kotlin.collections
 
+import kotlin.comparisons.*
+
 /**
  * Removes a single instance of the specified element from this
  * collection, if it is present.
@@ -171,11 +173,7 @@ public fun <T> MutableList<T>.removeAll(predicate: (T) -> Boolean): Boolean = fi
  */
 public fun <T> MutableList<T>.retainAll(predicate: (T) -> Boolean): Boolean = filterInPlace(predicate, false)
 
-@Fixme
 private fun <T> MutableList<T>.filterInPlace(predicate: (T) -> Boolean, predicateResultToRemove: Boolean): Boolean {
-    TODO()
-}
-/* TODO: fix downTo, RandomAccess
     if (this !is RandomAccess)
         return (this as MutableIterable<T>).filterInPlace(predicate, predicateResultToRemove)
 
@@ -199,97 +197,68 @@ private fun <T> MutableList<T>.filterInPlace(predicate: (T) -> Boolean, predicat
     else {
         return false
     }
-} */
+}
 
 /**
  * Removes all elements from this [MutableCollection] that are also contained in the given [elements] collection.
  */
-@Fixme
 public fun <T> MutableCollection<in T>.removeAll(elements: Iterable<T>): Boolean {
-    // TODO: add convertToSetForSetOperationWith
-    // return removeAll(elements.convertToSetForSetOperationWith(this))
-    var removed = false
-    for (e in elements) {
-        removed = removed or remove(e)
-    }
-    return removed
+    return removeAll(elements.convertToSetForSetOperationWith(this))
 }
 
 /**
  * Removes all elements from this [MutableCollection] that are also contained in the given [elements] sequence.
  */
-@Fixme
 public fun <T> MutableCollection<in T>.removeAll(elements: Sequence<T>): Boolean {
-    // TODO: add toHashSet()
-    //val set = elements.toHashSet()
-    // return set.isNotEmpty() && removeAll(set)
-    var removed = false
-    for (e in elements) {
-        removed = removed or remove(e)
-    }
-    return removed
+    val set = elements.toHashSet()
+    return set.isNotEmpty() && removeAll(set)
 }
 
 /**
  * Removes all elements from this [MutableCollection] that are also contained in the given [elements] array.
  */
-@Fixme
 public fun <T> MutableCollection<in T>.removeAll(elements: Array<out T>): Boolean {
-    // TODO: add toHashSet()
-    // return elements.isNotEmpty() && removeAll(elements.toHashSet())
-    var removed = false
-    for (e in elements) {
-        removed = removed or remove(e)
-    }
-    return removed
+    return elements.isNotEmpty() && removeAll(elements.toHashSet())
 }
 
 /**
  * Retains only elements of this [MutableCollection] that are contained in the given [elements] collection.
  */
-@Fixme
 public fun <T> MutableCollection<in T>.retainAll(elements: Iterable<T>): Boolean {
-    TODO()
-    //return retainAll(elements.convertToSetForSetOperationWith(this))
+    return retainAll(elements.convertToSetForSetOperationWith(this))
 }
 
 /**
  * Retains only elements of this [MutableCollection] that are contained in the given [elements] array.
  */
-@Fixme
 public fun <T> MutableCollection<in T>.retainAll(elements: Array<out T>): Boolean {
-    TODO()
-    //if (elements.isNotEmpty())
-    //    return retainAll(elements.toHashSet())
-    //else
-    //    return retainNothing()
+    if (elements.isNotEmpty())
+        return retainAll(elements.toHashSet())
+    else
+        return retainNothing()
 }
 
 /**
  * Retains only elements of this [MutableCollection] that are contained in the given [elements] sequence.
  */
-@Fixme
 public fun <T> MutableCollection<in T>.retainAll(elements: Sequence<T>): Boolean {
-    TODO()
-    //val set = elements.toHashSet()
-    //if (set.isNotEmpty())
-    //    return retainAll(set)
-    //else
-    //    return retainNothing()
+    val set = elements.toHashSet()
+    if (set.isNotEmpty())
+        return retainAll(set)
+    else
+        return retainNothing()
 }
 
-@Fixme
 private fun MutableCollection<*>.retainNothing(): Boolean {
-    TODO()
-    //val result = isNotEmpty()
-    //clear()
-    //return result
+    val result = isNotEmpty()
+    clear()
+    return result
 }
 
 /**
  * Sorts elements in the list in-place according to their natural sort order.
  */
-@Fixme
+@FixmeSorting
 public fun <T : Comparable<T>> MutableList<T>.sort(): Unit {
     TODO()
     //if (size > 1) java.util.Collections.sort(this)
@@ -298,6 +267,8 @@ public fun <T : Comparable<T>> MutableList<T>.sort(): Unit {
 /**
  * Sorts elements in the list in-place according to the order specified with [comparator].
  */
-//public fun <T> MutableList<T>.sortWith(comparator: Comparator<in T>): Unit {
-//if (size > 1) java.util.Collections.sort(this, comparator)
-//}
+@FixmeSorting
+public fun <T> MutableList<T>.sortWith(comparator: Comparator<in T>): Unit {
+    TODO()
+    //if (size > 1) java.util.Collections.sort(this, comparator)
+}

runtime/src/main/kotlin/kotlin/collections/RandomAccess.kt

@@ -0,0 +1,3 @@
+package kotlin.collections
+
+public interface RandomAccess

runtime/src/main/kotlin/kotlin/comparisons/Comparisons.kt

@@ -0,0 +1,300 @@
+package kotlin.comparisons
+
+interface Comparator<T> {
+    fun compare(a: T, b: T): Int
+}
+
+/**
+ * Compares two values using the specified functions [selectors] to calculate the result of the comparison.
+ * The functions are called sequentially, receive the given values [a] and [b] and return [Comparable]
+ * objects. As soon as the [Comparable] instances returned by a function for [a] and [b] values do not
+ * compare as equal, the result of that comparison is returned.
+ */
+public fun <T> compareValuesBy(a: T, b: T, vararg selectors: (T) -> Comparable<*>?): Int {
+    require(selectors.size > 0)
+    for (fn in selectors) {
+        val v1 = fn(a)
+        val v2 = fn(b)
+        val diff = compareValues(v1, v2)
+        if (diff != 0) return diff
+    }
+    return 0
+}
+
+/**
+ * Compares two values using the specified [selector] function to calculate the result of the comparison.
+ * The function is applied to the given values [a] and [b] and return [Comparable] objects.
+ * The result of comparison of these [Comparable] instances is returned.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T> compareValuesBy(a: T, b: T, selector: (T) -> Comparable<*>?): Int {
+    return compareValues(selector(a), selector(b))
+}
+
+/**
+ * Compares two values using the specified [selector] function to calculate the result of the comparison.
+ * The function is applied to the given values [a] and [b] and return objects of type K which are then being
+ * compared with the given [comparator].
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T, K> compareValuesBy(a: T, b: T, comparator: Comparator<in K>, selector: (T) -> K): Int {
+    return comparator.compare(selector(a), selector(b))
+}
+
+//// Not so useful without type inference for receiver of expression
+//// compareValuesWith(v1, v2, compareBy { it.prop1 } thenByDescending { it.prop2 })
+///**
+// * Compares two values using the specified [comparator].
+// */
+//@Suppress("NOTHING_TO_INLINE")
+//public inline fun <T> compareValuesWith(a: T, b: T, comparator: Comparator<T>): Int = comparator.compare(a, b)
+//
+
+
+/**
+ * Compares two nullable [Comparable] values. Null is considered less than any value.
+ */
+public fun <T : Comparable<*>> compareValues(a: T?, b: T?): Int {
+    if (a === b) return 0
+    if (a == null) return -1
+    if (b == null) return 1
+
+    @Suppress("UNCHECKED_CAST")
+    return (a as Comparable<Any>).compareTo(b)
+}
+
+/**
+ * Creates a comparator using the sequence of functions to calculate a result of comparison.
+ * The functions are called sequentially, receive the given values `a` and `b` and return [Comparable]
+ * objects. As soon as the [Comparable] instances returned by a function for `a` and `b` values do not
+ * compare as equal, the result of that comparison is returned from the [Comparator].
+ */
+public fun <T> compareBy(vararg selectors: (T) -> Comparable<*>?): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int = compareValuesBy(a, b, *selectors)
+    }
+}
+
+
+
+/**
+ * Creates a comparator using the function to transform value to a [Comparable] instance for comparison.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T> compareBy(crossinline selector: (T) -> Comparable<*>?): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int = compareValuesBy(a, b, selector)
+    }
+}
+
+/**
+ * Creates a comparator using the [selector] function to transform values being compared and then applying
+ * the specified [comparator] to compare transformed values.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T, K> compareBy(comparator: Comparator<in K>, crossinline selector: (T) -> K): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int = compareValuesBy(a, b, comparator, selector)
+    }
+}
+
+/**
+ * Creates a descending comparator using the function to transform value to a [Comparable] instance for comparison.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T> compareByDescending(crossinline selector: (T) -> Comparable<*>?): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int = compareValuesBy(b, a, selector)
+    }
+}
+
+/**
+ * Creates a descending comparator using the [selector] function to transform values being compared and then applying
+ * the specified [comparator] to compare transformed values.
+ *
+ * Note that an order of [comparator] is reversed by this wrapper.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T, K> compareByDescending(comparator: Comparator<in K>, crossinline selector: (T) -> K): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int = compareValuesBy(b, a, comparator, selector)
+    }
+}
+
+/**
+ * Creates a comparator comparing values after the primary comparator defined them equal. It uses
+ * the function to transform value to a [Comparable] instance for comparison.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T> Comparator<T>.thenBy(crossinline selector: (T) -> Comparable<*>?): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int {
+            val previousCompare = this@thenBy.compare(a, b)
+            return if (previousCompare != 0) previousCompare else compareValuesBy(a, b, selector)
+        }
+    }
+}
+
+/**
+ * Creates a comparator comparing values after the primary comparator defined them equal. It uses
+ * the [selector] function to transform values and then compares them with the given [comparator].
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T, K> Comparator<T>.thenBy(comparator: Comparator<in K>, crossinline selector: (T) -> K): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int {
+            val previousCompare = this@thenBy.compare(a, b)
+            return if (previousCompare != 0) previousCompare else compareValuesBy(a, b, comparator, selector)
+        }
+    }
+}
+
+/**
+ * Creates a descending comparator using the primary comparator and
+ * the function to transform value to a [Comparable] instance for comparison.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T> Comparator<T>.thenByDescending(crossinline selector: (T) -> Comparable<*>?): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int {
+            val previousCompare = this@thenByDescending.compare(a, b)
+            return if (previousCompare != 0) previousCompare else compareValuesBy(b, a, selector)
+        }
+    }
+}
+
+/**
+ * Creates a descending comparator comparing values after the primary comparator defined them equal. It uses
+ * the [selector] function to transform values and then compares them with the given [comparator].
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T, K> Comparator<T>.thenByDescending(comparator: Comparator<in K>, crossinline selector: (T) -> K): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int {
+            val previousCompare = this@thenByDescending.compare(a, b)
+            return if (previousCompare != 0) previousCompare else compareValuesBy(b, a, comparator, selector)
+        }
+    }
+}
+
+
+/**
+ * Creates a comparator using the primary comparator and function to calculate a result of comparison.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T> Comparator<T>.thenComparator(crossinline comparison: (T, T) -> Int): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int {
+            val previousCompare = this@thenComparator.compare(a, b)
+            return if (previousCompare != 0) previousCompare else comparison(a, b)
+        }
+    }
+}
+
+/**
+ * Combines this comparator and the given [comparator] such that the latter is applied only
+ * when the former considered values equal.
+ */
+public infix fun <T> Comparator<T>.then(comparator: Comparator<in T>): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int {
+            val previousCompare = this@then.compare(a, b)
+            return if (previousCompare != 0) previousCompare else comparator.compare(a, b)
+        }
+    }
+}
+
+/**
+ * Combines this comparator and the given [comparator] such that the latter is applied only
+ * when the former considered values equal.
+ */
+public infix fun <T> Comparator<T>.thenDescending(comparator: Comparator<in T>): Comparator<T> {
+    return object : Comparator<T> {
+        public override fun compare(a: T, b: T): Int {
+            val previousCompare = this@thenDescending.compare(a, b)
+            return if (previousCompare != 0) previousCompare else comparator.compare(b, a)
+        }
+    }
+}
+
+// Not so useful without type inference for receiver of expression
+/**
+ * Extends the given [comparator] of non-nullable values to a comparator of nullable values
+ * considering `null` value less than any other value.
+ */
+public fun <T: Any> nullsFirst(comparator: Comparator<in T>): Comparator<T?> {
+    return object: Comparator<T?> {
+        override fun compare(a: T?, b: T?): Int {
+            if (a === b) return 0
+            if (a == null) return -1
+            if (b == null) return 1
+            return comparator.compare(a, b)
+        }
+    }
+}
+
+/**
+ * Provides a comparator of nullable [Comparable] values
+ * considering `null` value less than any other value.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T: Comparable<T>> nullsFirst(): Comparator<T?> = nullsFirst(naturalOrder())
+
+/**
+ * Extends the given [comparator] of non-nullable values to a comparator of nullable values
+ * considering `null` value greater than any other value.
+ */
+public fun <T: Any> nullsLast(comparator: Comparator<in T>): Comparator<T?> {
+    return object: Comparator<T?> {
+        override fun compare(a: T?, b: T?): Int {
+            if (a === b) return 0
+            if (a == null) return 1
+            if (b == null) return -1
+            return comparator.compare(a, b)
+        }
+    }
+}
+
+/**
+ * Provides a comparator of nullable [Comparable] values
+ * considering `null` value greater than any other value.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T: Comparable<T>> nullsLast(): Comparator<T?> = nullsLast(naturalOrder())
+
+/**
+ * Returns a comparator that compares [Comparable] objects in natural order.
+ */
+public fun <T: Comparable<T>> naturalOrder(): Comparator<T> = @Suppress("UNCHECKED_CAST") (NaturalOrderComparator as Comparator<T>)
+
+/**
+ * Returns a comparator that compares [Comparable] objects in reversed natural order.
+ */
+public fun <T: Comparable<T>> reverseOrder(): Comparator<T> = @Suppress("UNCHECKED_CAST") (ReverseOrderComparator as Comparator<T>)
+
+/** Returns a comparator that imposes the reverse ordering of this comparator. */
+public fun <T> Comparator<T>.reversed(): Comparator<T> = when (this) {
+    is ReversedComparator -> this.comparator
+    NaturalOrderComparator -> @Suppress("UNCHECKED_CAST") (ReverseOrderComparator as Comparator<T>)
+    ReverseOrderComparator -> @Suppress("UNCHECKED_CAST") (NaturalOrderComparator as Comparator<T>)
+    else -> ReversedComparator(this)
+}
+
+
+private class ReversedComparator<T>(public val comparator: Comparator<T>): Comparator<T> {
+    override fun compare(a: T, b: T): Int = comparator.compare(b, a)
+    @Suppress("VIRTUAL_MEMBER_HIDDEN")
+    fun reversed(): Comparator<T> = comparator
+}
+
+private object NaturalOrderComparator : Comparator<Comparable<Any>> {
+    override fun compare(a: Comparable<Any>, b: Comparable<Any>): Int = a.compareTo(b)
+    @Suppress("VIRTUAL_MEMBER_HIDDEN")
+    fun reversed(): Comparator<Comparable<Any>> = ReverseOrderComparator
+}
+
+private object ReverseOrderComparator: Comparator<Comparable<Any>> {
+    override fun compare(a: Comparable<Any>, b: Comparable<Any>): Int = b.compareTo(a)
+    @Suppress("VIRTUAL_MEMBER_HIDDEN")
+    fun reversed(): Comparator<Comparable<Any>> = NaturalOrderComparator
+}

runtime/src/main/kotlin/kotlin/ranges/Ranges.kt

@@ -333,3 +333,12 @@ public fun Long.coerceIn(range: ClosedRange<Long>): Long {
 public fun IntProgression.reversed(): IntProgression {
     return IntProgression.fromClosedRange(last, first, -step)
 }
+
+/**
+ * Returns a progression from this value down to the specified [to] value with the step -1.
+ *
+ * The [to] value has to be less than this value.
+ */
+public infix fun Int.downTo(to: Int): IntProgression {
+    return IntProgression.fromClosedRange(this, to, -1)
+}

runtime/src/main/kotlin/kotlin/sequences/Sequence.kt

@@ -21,3 +21,22 @@ public interface Sequence<out T> {
      */
     public operator fun iterator(): Iterator<T>
 }
+
+/**
+ * A sequence that supports drop(n) and take(n) operations
+ */
+internal interface DropTakeSequence<T> : Sequence<T> {
+    fun drop(n: Int): Sequence<T>
+    fun take(n: Int): Sequence<T>
+}
+
+/**
+ * Returns an empty sequence.
+ */
+public fun <T> emptySequence(): Sequence<T> = EmptySequence
+
+private object EmptySequence : Sequence<Nothing>, DropTakeSequence<Nothing> {
+    override fun iterator(): Iterator<Nothing> = EmptyIterator
+    override fun drop(n: Int) = EmptySequence
+    override fun take(n: Int) = EmptySequence
+}

runtime/src/main/kotlin/kotlin/text/Appendable.kt

@@ -0,0 +1,7 @@
+package kotlin.text
+
+interface Appendable {
+    fun append(c: Char): Appendable
+    fun append(csq: CharSequence?): Appendable
+    fun append(csq: CharSequence?, start: Int, end: Int): Appendable
+}

runtime/src/main/kotlin/kotlin/text/StringBuilder.kt

@@ -13,7 +13,7 @@ external fun toCharArray(string: String) : CharArray
 
 class StringBuilder private constructor (
         private var array: CharArray
-) : CharSequence {
+) : CharSequence, Appendable {
     constructor() : this(10)
 
     constructor(capacity: Int) : this(CharArray(capacity))
@@ -57,11 +57,17 @@ class StringBuilder private constructor (
         }
     }
 
-    fun append(it: Char) {
+    // Of Appenable.
+    override fun append(c: Char) : Appendable {
         ensureExtraCapacity(1)
-        array[length++] = it
+        array[length++] = c
+        return this
     }
 
+    override fun append(csq: CharSequence?): Appendable = TODO()
+
+    override fun append(csq: CharSequence?, start: Int, end: Int): Appendable = TODO()
+
     fun append(it: CharArray) {
         ensureExtraCapacity(it.size)
         for (c in it)

runtime/src/main/kotlin/kotlin/util/Preconditions.kt

@@ -0,0 +1,98 @@
+package kotlin
+
+/**
+ * Throws an [IllegalArgumentException] if the [value] is false.
+ *
+ * @sample samples.misc.Preconditions.failRequireWithLazyMessage
+ */
+@kotlin.internal.InlineOnly
+public inline fun require(value: Boolean): Unit = require(value) { "Failed requirement." }
+
+/**
+ * Throws an [IllegalArgumentException] with the result of calling [lazyMessage] if the [value] is false.
+ *
+ * @sample samples.misc.Preconditions.failRequireWithLazyMessage
+ */
+@kotlin.internal.InlineOnly
+public inline fun require(value: Boolean, lazyMessage: () -> Any): Unit {
+    if (!value) {
+        val message = lazyMessage()
+        throw IllegalArgumentException(message.toString())
+    }
+}
+
+/**
+ * Throws an [IllegalArgumentException] if the [value] is null. Otherwise returns the not null value.
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T:Any> requireNotNull(value: T?): T = requireNotNull(value) { "Required value was null." }
+
+/**
+ * Throws an [IllegalArgumentException] with the result of calling [lazyMessage] if the [value] is null. Otherwise
+ * returns the not null value.
+ *
+ * @sample samples.misc.Preconditions.failRequireWithLazyMessage
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T:Any> requireNotNull(value: T?, lazyMessage: () -> Any): T {
+    if (value == null) {
+        val message = lazyMessage()
+        throw IllegalArgumentException(message.toString())
+    } else {
+        return value
+    }
+}
+
+/**
+ * Throws an [IllegalStateException] if the [value] is false.
+ *
+ * @sample samples.misc.Preconditions.failCheckWithLazyMessage
+ */
+@kotlin.internal.InlineOnly
+public inline fun check(value: Boolean): Unit = check(value) { "Check failed." }
+
+/**
+ * Throws an [IllegalStateException] with the result of calling [lazyMessage] if the [value] is false.
+ *
+ * @sample samples.misc.Preconditions.failCheckWithLazyMessage
+ */
+@kotlin.internal.InlineOnly
+public inline fun check(value: Boolean, lazyMessage: () -> Any): Unit {
+    if (!value) {
+        val message = lazyMessage()
+        throw IllegalStateException(message.toString())
+    }
+}
+
+/**
+ * Throws an [IllegalStateException] if the [value] is null. Otherwise
+ * returns the not null value.
+ *
+ * @sample samples.misc.Preconditions.failCheckWithLazyMessage
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T:Any> checkNotNull(value: T?): T = checkNotNull(value) { "Required value was null." }
+
+/**
+ * Throws an [IllegalStateException] with the result of calling [lazyMessage]  if the [value] is null. Otherwise
+ * returns the not null value.
+ *
+ * @sample samples.misc.Preconditions.failCheckWithLazyMessage
+ */
+@kotlin.internal.InlineOnly
+public inline fun <T:Any> checkNotNull(value: T?, lazyMessage: () -> Any): T {
+    if (value == null) {
+        val message = lazyMessage()
+        throw IllegalStateException(message.toString())
+    } else {
+        return value
+    }
+}
+
+/**
+ * Throws an [IllegalStateException] with the given [message].
+ *
+ * @sample samples.misc.Preconditions.failWithError
+ */
+@kotlin.internal.InlineOnly
+public inline fun error(message: Any): Nothing = throw IllegalStateException(message.toString())