sdk/lib/collection/iterable.dart

// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

part of dart.collection;

/**
 * This [Iterable] mixin implements all [Iterable] members except `iterator`.
 *
 * All other methods are implemented in terms of `iterator`.
 */
abstract class IterableMixin<E> implements Iterable<E> {
  Iterable map(f(E element)) => new MappedIterable<E, dynamic>(this, f);

  Iterable<E> where(bool f(E element)) => new WhereIterable<E>(this, f);

  Iterable expand(Iterable f(E element)) =>
      new ExpandIterable<E, dynamic>(this, f);

  bool contains(Object element) {
    for (E e in this) {
      if (e == element) return true;
    }
    return false;
  }

  void forEach(void f(E element)) {
    for (E element in this) f(element);
  }

  E reduce(E combine(E value, E element)) {
    Iterator<E> iterator = this.iterator;
    if (!iterator.moveNext()) {
      throw new StateError("No elements");
    }
    E value = iterator.current;
    while (iterator.moveNext()) {
      value = combine(value, iterator.current);
    }
    return value;
  }

  dynamic fold(var initialValue,
               dynamic combine(var previousValue, E element)) {
    var value = initialValue;
    for (E element in this) value = combine(value, element);
    return value;
  }

  bool every(bool f(E element)) {
    for (E element in this) {
      if (!f(element)) return false;
    }
    return true;
  }

  String join([String separator = ""]) {
    Iterator<E> iterator = this.iterator;
    if (!iterator.moveNext()) return "";
    StringBuffer buffer = new StringBuffer();
    if (separator == null || separator == "") {
      do {
        buffer.write("${iterator.current}");
      } while (iterator.moveNext());
    } else {
      buffer.write("${iterator.current}");
      while (iterator.moveNext()) {
        buffer.write(separator);
        buffer.write("${iterator.current}");
      }
    }
    return buffer.toString();
  }

  bool any(bool f(E element)) {
    for (E element in this) {
      if (f(element)) return true;
    }
    return false;
  }

  List<E> toList({ bool growable: true }) =>
      new List<E>.from(this, growable: growable);

  Set<E> toSet() => new Set<E>.from(this);

  int get length {
    int count = 0;
    Iterator it = iterator;
    while (it.moveNext()) {
      count++;
    }
    return count;
  }

  bool get isEmpty => !iterator.moveNext();

  bool get isNotEmpty => !isEmpty;

  Iterable<E> take(int n) {
    return new TakeIterable<E>(this, n);
  }

  Iterable<E> takeWhile(bool test(E value)) {
    return new TakeWhileIterable<E>(this, test);
  }

  Iterable<E> skip(int n) {
    return new SkipIterable<E>(this, n);
  }

  Iterable<E> skipWhile(bool test(E value)) {
    return new SkipWhileIterable<E>(this, test);
  }

  E get first {
    Iterator it = iterator;
    if (!it.moveNext()) {
      throw new StateError("No elements");
    }
    return it.current;
  }

  E get last {
    Iterator it = iterator;
    if (!it.moveNext()) {
      throw new StateError("No elements");
    }
    E result;
    do {
      result = it.current;
    } while(it.moveNext());
    return result;
  }

  E get single {
    Iterator it = iterator;
    if (!it.moveNext()) throw new StateError("No elements");
    E result = it.current;
    if (it.moveNext()) throw new StateError("More than one element");
    return result;
  }

  dynamic firstWhere(bool test(E value), { Object orElse() }) {
    for (E element in this) {
      if (test(element)) return element;
    }
    if (orElse != null) return orElse();
    throw new StateError("No matching element");
  }

  dynamic lastWhere(bool test(E value), { Object orElse() }) {
    E result = null;
    bool foundMatching = false;
    for (E element in this) {
      if (test(element)) {
        result = element;
        foundMatching = true;
      }
    }
    if (foundMatching) return result;
    if (orElse != null) return orElse();
    throw new StateError("No matching element");
  }

  E singleWhere(bool test(E value)) {
    E result = null;
    bool foundMatching = false;
    for (E element in this) {
      if (test(element)) {
        if (foundMatching) {
          throw new StateError("More than one matching element");
        }
        result = element;
        foundMatching = true;
      }
    }
    if (foundMatching) return result;
    throw new StateError("No matching element");
  }

  E elementAt(int index) {
    if (index is! int || index < 0) throw new RangeError.value(index);
    int remaining = index;
    for (E element in this) {
      if (remaining == 0) return element;
      remaining--;
    }
    throw new RangeError.value(index);
  }
}

/**
 * Base class for implementing [Iterable].
 *
 * This class implements all methods of [Iterable] except [Iterable.iterator]
 * in terms of `iterator`.
 */
abstract class IterableBase<E> implements Iterable<E> {
  // TODO(lrn): Base this on IterableMixin if there ever becomes a way
  // to combine const constructors and mixins.
  const IterableBase();

  Iterable map(f(E element)) => new MappedIterable<E, dynamic>(this, f);

  Iterable<E> where(bool f(E element)) => new WhereIterable<E>(this, f);

  Iterable expand(Iterable f(E element)) =>
      new ExpandIterable<E, dynamic>(this, f);

  bool contains(Object element) {
    for (E e in this) {
      if (e == element) return true;
    }
    return false;
  }

  void forEach(void f(E element)) {
    for (E element in this) f(element);
  }

  E reduce(E combine(E value, E element)) {
    Iterator<E> iterator = this.iterator;
    if (!iterator.moveNext()) {
      throw new StateError("No elements");
    }
    E value = iterator.current;
    while (iterator.moveNext()) {
      value = combine(value, iterator.current);
    }
    return value;
  }

  dynamic fold(var initialValue,
               dynamic combine(var previousValue, E element)) {
    var value = initialValue;
    for (E element in this) value = combine(value, element);
    return value;
  }

  bool every(bool f(E element)) {
    for (E element in this) {
      if (!f(element)) return false;
    }
    return true;
  }

  String join([String separator = ""]) {
    Iterator<E> iterator = this.iterator;
    if (!iterator.moveNext()) return "";
    StringBuffer buffer = new StringBuffer();
    if (separator == null || separator == "") {
      do {
        buffer.write("${iterator.current}");
      } while (iterator.moveNext());
    } else {
      buffer.write("${iterator.current}");
      while (iterator.moveNext()) {
        buffer.write(separator);
        buffer.write("${iterator.current}");
      }
    }
    return buffer.toString();
  }

  bool any(bool f(E element)) {
    for (E element in this) {
      if (f(element)) return true;
    }
    return false;
  }

  List<E> toList({ bool growable: true }) =>
      new List<E>.from(this, growable: growable);

  Set<E> toSet() => new Set<E>.from(this);

  int get length {
    int count = 0;
    Iterator it = iterator;
    while (it.moveNext()) {
      count++;
    }
    return count;
  }

  bool get isEmpty => !iterator.moveNext();

  bool get isNotEmpty => !isEmpty;

  Iterable<E> take(int n) {
    return new TakeIterable<E>(this, n);
  }

  Iterable<E> takeWhile(bool test(E value)) {
    return new TakeWhileIterable<E>(this, test);
  }

  Iterable<E> skip(int n) {
    return new SkipIterable<E>(this, n);
  }

  Iterable<E> skipWhile(bool test(E value)) {
    return new SkipWhileIterable<E>(this, test);
  }

  E get first {
    Iterator it = iterator;
    if (!it.moveNext()) {
      throw new StateError("No elements");
    }
    return it.current;
  }

  E get last {
    Iterator it = iterator;
    if (!it.moveNext()) {
      throw new StateError("No elements");
    }
    E result;
    do {
      result = it.current;
    } while(it.moveNext());
    return result;
  }

  E get single {
    Iterator it = iterator;
    if (!it.moveNext()) throw new StateError("No elements");
    E result = it.current;
    if (it.moveNext()) throw new StateError("More than one element");
    return result;
  }

  dynamic firstWhere(bool test(E value), { Object orElse() }) {
    for (E element in this) {
      if (test(element)) return element;
    }
    if (orElse != null) return orElse();
    throw new StateError("No matching element");
  }

  dynamic lastWhere(bool test(E value), { Object orElse() }) {
    E result = null;
    bool foundMatching = false;
    for (E element in this) {
      if (test(element)) {
        result = element;
        foundMatching = true;
      }
    }
    if (foundMatching) return result;
    if (orElse != null) return orElse();
    throw new StateError("No matching element");
  }

  E singleWhere(bool test(E value)) {
    E result = null;
    bool foundMatching = false;
    for (E element in this) {
      if (test(element)) {
        if (foundMatching) {
          throw new StateError("More than one matching element");
        }
        result = element;
        foundMatching = true;
      }
    }
    if (foundMatching) return result;
    throw new StateError("No matching element");
  }

  E elementAt(int index) {
    if (index is! int || index < 0) throw new RangeError.value(index);
    int remaining = index;
    for (E element in this) {
      if (remaining == 0) return element;
      remaining--;
    }
    throw new RangeError.value(index);
  }
}