quiver/lib/src/iterables/min_max.dart

// Copyright 2013 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

part of quiver.iterables;

/**
 * Returns the maximum value in [i], according to the order specified by the
 * [compare] function, or `null` if [i] is empty.
 *
 * The compare function must act as a [Comparator]. If [compare] is omitted,
 * [Comparable.compare] is used. If [i] contains null elements, an exception
 * will be thrown.
 *
 */
dynamic max(Iterable i, [Comparator compare = Comparable.compare]) =>
    i.isEmpty ? null : i.reduce((a, b) => compare(a, b) > 0 ? a : b);

/**
 * Returns the minimum value in [i], according to the order specified by the
 * [compare] function, or `null` if [i] is empty.
 *
 * The compare function must act as a [Comparator]. If [compare] is omitted,
 * [Comparable.compare] is used. If [i] contains null elements, an exception
 * will be thrown.
 */
dynamic min(Iterable i, [Comparator compare = Comparable.compare]) =>
    i.isEmpty ? null : i.reduce((a, b) => compare(a, b) < 0 ? a : b);

/**
 * Returns the minimum and maximum values in [i], according to the order
 * specified by the [compare] function, in an [Extent] instance. Always returns
 * an [Extent], but [Extent.min] and [Extent.max] may be `null` if [i] is empty.
 *
 * The compare function must act as a [Comparator]. If [compare] is omitted,
 * [Comparable.compare] is used. If [i] contains null elements, an exception
 * will be thrown.
 *
 * If [i] is empty, an [Extent] is returned with [:null:] values for [:min:] and
 * [:max:], since there are no valid values for them.
 */
Extent extent(Iterable i, [Comparator compare = Comparable.compare]) {
  var iterator = i.iterator;
  var hasNext = iterator.moveNext();
  if (!hasNext) return new Extent(null, null);
  var max = iterator.current;
  var min = iterator.current;
  while (iterator.moveNext()) {
    if (compare(max, iterator.current) < 0) max = iterator.current;
    if (compare(min, iterator.current) > 0) min = iterator.current;
  }
  return new Extent(min, max);
}

class Extent {
  final min;
  final max;
  Extent(this.min, this.max);
}