array.ts

/*-----------------------------------------------------------------------------
| Copyright (c) 2014-2017, PhosphorJS Contributors
|
| Distributed under the terms of the BSD 3-Clause License.
|
| The full license is in the file LICENSE, distributed with this software.
|----------------------------------------------------------------------------*/


/**
 * The namespace for array-specific algorithms.
 */
export
namespace ArrayExt {
  /**
   * Find the index of the first occurrence of a value in an array.
   *
   * @param array - The array-like object to search.
   *
   * @param value - The value to locate in the array. Values are
   *   compared using strict `===` equality.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The index of the first occurrence of the value, or `-1`
   *   if the value is not found.
   *
   * #### Notes
   * If `stop < start` the search will wrap at the end of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * A `start` or `stop` which is non-integral.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let data = ['one', 'two', 'three', 'four', 'one'];
   * ArrayExt.firstIndexOf(data, 'red');        // -1
   * ArrayExt.firstIndexOf(data, 'one');        // 0
   * ArrayExt.firstIndexOf(data, 'one', 1);     // 4
   * ArrayExt.firstIndexOf(data, 'two', 2);     // -1
   * ArrayExt.firstIndexOf(data, 'two', 2, 1);  // 1
   * ```
   */
  export
  function firstIndexOf<T>(array: ArrayLike<T>, value: T, start = 0, stop = -1): number {
    let n = array.length;
    if (n === 0) {
      return -1;
    }
    if (start < 0) {
      start = Math.max(0, start + n);
    } else {
      start = Math.min(start, n - 1);
    }
    if (stop < 0) {
      stop = Math.max(0, stop + n);
    } else {
      stop = Math.min(stop, n - 1);
    }
    let span: number;
    if (stop < start) {
      span = (stop + 1) + (n - start);
    } else {
      span = stop - start + 1;
    }
    for (let i = 0; i < span; ++i) {
      let j = (start + i) % n;
      if (array[j] === value) {
        return j;
      }
    }
    return -1;
  }

  /**
   * Find the index of the last occurrence of a value in an array.
   *
   * @param array - The array-like object to search.
   *
   * @param value - The value to locate in the array. Values are
   *   compared using strict `===` equality.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The index of the last occurrence of the value, or `-1`
   *   if the value is not found.
   *
   * #### Notes
   * If `start < stop` the search will wrap at the front of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * A `start` or `stop` which is non-integral.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let data = ['one', 'two', 'three', 'four', 'one'];
   * ArrayExt.lastIndexOf(data, 'red');        // -1
   * ArrayExt.lastIndexOf(data, 'one');        // 4
   * ArrayExt.lastIndexOf(data, 'one', 1);     // 0
   * ArrayExt.lastIndexOf(data, 'two', 0);     // -1
   * ArrayExt.lastIndexOf(data, 'two', 0, 1);  // 1
   * ```
   */
  export
  function lastIndexOf<T>(array: ArrayLike<T>, value: T, start = -1, stop = 0): number {
    let n = array.length;
    if (n === 0) {
      return -1;
    }
    if (start < 0) {
      start = Math.max(0, start + n);
    } else {
      start = Math.min(start, n - 1);
    }
    if (stop < 0) {
      stop = Math.max(0, stop + n);
    } else {
      stop = Math.min(stop, n - 1);
    }
    let span: number;
    if (start < stop) {
      span = (start + 1) + (n - stop);
    } else {
      span = start - stop + 1;
    }
    for (let i = 0; i < span; ++i) {
      let j = (start - i + n) % n;
      if (array[j] === value) {
        return j;
      }
    }
    return -1;
  }

  /**
   * Find the index of the first value which matches a predicate.
   *
   * @param array - The array-like object to search.
   *
   * @param fn - The predicate function to apply to the values.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The index of the first matching value, or `-1` if no
   *   matching value is found.
   *
   * #### Notes
   * If `stop < start` the search will wrap at the end of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * A `start` or `stop` which is non-integral.
   *
   * Modifying the length of the array while searching.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * function isEven(value: number): boolean {
   *   return value % 2 === 0;
   * }
   *
   * let data = [1, 2, 3, 4, 3, 2, 1];
   * ArrayExt.findFirstIndex(data, isEven);       // 1
   * ArrayExt.findFirstIndex(data, isEven, 4);    // 5
   * ArrayExt.findFirstIndex(data, isEven, 6);    // -1
   * ArrayExt.findFirstIndex(data, isEven, 6, 5); // 1
   * ```
   */
  export
  function findFirstIndex<T>(array: ArrayLike<T>, fn: (value: T, index: number) => boolean, start = 0, stop = -1): number {
    let n = array.length;
    if (n === 0) {
      return -1;
    }
    if (start < 0) {
      start = Math.max(0, start + n);
    } else {
      start = Math.min(start, n - 1);
    }
    if (stop < 0) {
      stop = Math.max(0, stop + n);
    } else {
      stop = Math.min(stop, n - 1);
    }
    let span: number;
    if (stop < start) {
      span = (stop + 1) + (n - start);
    } else {
      span = stop - start + 1;
    }
    for (let i = 0; i < span; ++i) {
      let j = (start + i) % n;
      if (fn(array[j], j)) {
        return j;
      }
    }
    return -1;
  }

  /**
   * Find the index of the last value which matches a predicate.
   *
   * @param object - The array-like object to search.
   *
   * @param fn - The predicate function to apply to the values.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The index of the last matching value, or `-1` if no
   *   matching value is found.
   *
   * #### Notes
   * If `start < stop` the search will wrap at the front of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * A `start` or `stop` which is non-integral.
   *
   * Modifying the length of the array while searching.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * function isEven(value: number): boolean {
   *   return value % 2 === 0;
   * }
   *
   * let data = [1, 2, 3, 4, 3, 2, 1];
   * ArrayExt.findLastIndex(data, isEven);        // 5
   * ArrayExt.findLastIndex(data, isEven, 4);     // 3
   * ArrayExt.findLastIndex(data, isEven, 0);     // -1
   * ArrayExt.findLastIndex(data, isEven, 0, 1);  // 5
   * ```
   */
  export
  function findLastIndex<T>(array: ArrayLike<T>, fn: (value: T, index: number) => boolean, start = -1, stop = 0): number {
    let n = array.length;
    if (n === 0) {
      return -1;
    }
    if (start < 0) {
      start = Math.max(0, start + n);
    } else {
      start = Math.min(start, n - 1);
    }
    if (stop < 0) {
      stop = Math.max(0, stop + n);
    } else {
      stop = Math.min(stop, n - 1);
    }
    let d: number;
    if (start < stop) {
      d = (start + 1) + (n - stop);
    } else {
      d = start - stop + 1;
    }
    for (let i = 0; i < d; ++i) {
      let j = (start - i + n) % n;
      if (fn(array[j], j)) {
        return j;
      }
    }
    return -1;
  }

  /**
   * Find the first value which matches a predicate.
   *
   * @param array - The array-like object to search.
   *
   * @param fn - The predicate function to apply to the values.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The first matching value, or `undefined` if no matching
   *   value is found.
   *
   * #### Notes
   * If `stop < start` the search will wrap at the end of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * A `start` or `stop` which is non-integral.
   *
   * Modifying the length of the array while searching.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * function isEven(value: number): boolean {
   *   return value % 2 === 0;
   * }
   *
   * let data = [1, 2, 3, 4, 3, 2, 1];
   * ArrayExt.findFirstValue(data, isEven);       // 2
   * ArrayExt.findFirstValue(data, isEven, 2);    // 4
   * ArrayExt.findFirstValue(data, isEven, 6);    // undefined
   * ArrayExt.findFirstValue(data, isEven, 6, 5); // 2
   * ```
   */
  export
  function findFirstValue<T>(array: ArrayLike<T>, fn: (value: T, index: number) => boolean, start = 0, stop = -1): T | undefined {
    let index = findFirstIndex(array, fn, start, stop);
    return index !== -1 ? array[index] : undefined;
  }

  /**
   * Find the last value which matches a predicate.
   *
   * @param object - The array-like object to search.
   *
   * @param fn - The predicate function to apply to the values.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The last matching value, or `undefined` if no matching
   *   value is found.
   *
   * #### Notes
   * If `start < stop` the search will wrap at the front of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * A `start` or `stop` which is non-integral.
   *
   * Modifying the length of the array while searching.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * function isEven(value: number): boolean {
   *   return value % 2 === 0;
   * }
   *
   * let data = [1, 2, 3, 4, 3, 2, 1];
   * ArrayExt.findLastValue(data, isEven);        // 2
   * ArrayExt.findLastValue(data, isEven, 4);     // 4
   * ArrayExt.findLastValue(data, isEven, 0);     // undefined
   * ArrayExt.findLastValue(data, isEven, 0, 1);  // 2
   * ```
   */
  export
  function findLastValue<T>(array: ArrayLike<T>, fn: (value: T, index: number) => boolean, start = -1, stop = 0): T | undefined {
    let index = findLastIndex(array, fn, start, stop);
    return index !== -1 ? array[index] : undefined;
  }

  /**
   * Find the index of the first element which compares `>=` to a value.
   *
   * @param array - The sorted array-like object to search.
   *
   * @param value - The value to locate in the array.
   *
   * @param fn - The 3-way comparison function to apply to the values.
   *   It should return `< 0` if an element is less than a value, `0` if
   *   an element is equal to a value, or `> 0` if an element is greater
   *   than a value.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The index of the first element which compares `>=` to the
   *   value, or `length` if there is no such element. If the computed
   *   index for `stop` is less than `start`, then the computed index
   *   for `start` is returned.
   *
   * #### Notes
   * The array must already be sorted in ascending order according to
   * the comparison function.
   *
   * #### Complexity
   * Logarithmic.
   *
   * #### Undefined Behavior
   * Searching a range which is not sorted in ascending order.
   *
   * A `start` or `stop` which is non-integral.
   *
   * Modifying the length of the array while searching.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * function numberCmp(a: number, b: number): number {
   *   return a - b;
   * }
   *
   * let data = [0, 3, 4, 7, 7, 9];
   * ArrayExt.lowerBound(data, 0, numberCmp);   // 0
   * ArrayExt.lowerBound(data, 6, numberCmp);   // 3
   * ArrayExt.lowerBound(data, 7, numberCmp);   // 3
   * ArrayExt.lowerBound(data, -1, numberCmp);  // 0
   * ArrayExt.lowerBound(data, 10, numberCmp);  // 6
   * ```
   */
  export
  function lowerBound<T, U>(array: ArrayLike<T>, value: U, fn: (element: T, value: U) => number, start = 0, stop = -1): number {
    let n = array.length;
    if (n === 0) {
      return 0;
    }
    if (start < 0) {
      start = Math.max(0, start + n);
    } else {
      start = Math.min(start, n - 1);
    }
    if (stop < 0) {
      stop = Math.max(0, stop + n);
    } else {
      stop = Math.min(stop, n - 1);
    }
    let begin = start;
    let span = stop - start + 1;
    while (span > 0) {
      let half = span >> 1;
      let middle = begin + half;
      if (fn(array[middle], value) < 0) {
        begin = middle + 1;
        span -= half + 1;
      } else {
        span = half;
      }
    }
    return begin;
  }

  /**
   * Find the index of the first element which compares `>` than a value.
   *
   * @param array - The sorted array-like object to search.
   *
   * @param value - The value to locate in the array.
   *
   * @param fn - The 3-way comparison function to apply to the values.
   *   It should return `< 0` if an element is less than a value, `0` if
   *   an element is equal to a value, or `> 0` if an element is greater
   *   than a value.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The index of the first element which compares `>` than the
   *   value, or `length` if there is no such element. If the computed
   *   index for `stop` is less than `start`, then the computed index
   *   for `start` is returned.
   *
   * #### Notes
   * The array must already be sorted in ascending order according to
   * the comparison function.
   *
   * #### Complexity
   * Logarithmic.
   *
   * #### Undefined Behavior
   * Searching a range which is not sorted in ascending order.
   *
   * A `start` or `stop` which is non-integral.
   *
   * Modifying the length of the array while searching.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * function numberCmp(a: number, b: number): number {
   *   return a - b;
   * }
   *
   * let data = [0, 3, 4, 7, 7, 9];
   * ArrayExt.upperBound(data, 0, numberCmp);   // 1
   * ArrayExt.upperBound(data, 6, numberCmp);   // 3
   * ArrayExt.upperBound(data, 7, numberCmp);   // 5
   * ArrayExt.upperBound(data, -1, numberCmp);  // 0
   * ArrayExt.upperBound(data, 10, numberCmp);  // 6
   * ```
   */
  export
  function upperBound<T, U>(array: ArrayLike<T>, value: U, fn: (element: T, value: U) => number, start = 0, stop = -1): number {
    let n = array.length;
    if (n === 0) {
      return 0;
    }
    if (start < 0) {
      start = Math.max(0, start + n);
    } else {
      start = Math.min(start, n - 1);
    }
    if (stop < 0) {
      stop = Math.max(0, stop + n);
    } else {
      stop = Math.min(stop, n - 1);
    }
    let begin = start;
    let span = stop - start + 1;
    while (span > 0) {
      let half = span >> 1;
      let middle = begin + half;
      if (fn(array[middle], value) > 0) {
        span = half;
      } else {
        begin = middle + 1;
        span -= half + 1;
      }
    }
    return begin;
  }

  /**
   * Test whether two arrays are shallowly equal.
   *
   * @param a - The first array-like object to compare.
   *
   * @param b - The second array-like object to compare.
   *
   * @param fn - The comparison function to apply to the elements. It
   *   should return `true` if the elements are "equal". The default
   *   compares elements using strict `===` equality.
   *
   * @returns Whether the two arrays are shallowly equal.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * Modifying the length of the arrays while comparing.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let d1 = [0, 3, 4, 7, 7, 9];
   * let d2 = [0, 3, 4, 7, 7, 9];
   * let d3 = [42];
   * ArrayExt.shallowEqual(d1, d2);  // true
   * ArrayExt.shallowEqual(d2, d3);  // false
   * ```
   */
  export
  function shallowEqual<T>(a: ArrayLike<T>, b: ArrayLike<T>, fn?: (a: T, b: T) => boolean): boolean {
    // Check for object identity first.
    if (a === b) {
      return true;
    }

    // Bail early if the lengths are different.
    if (a.length !== b.length) {
      return false;
    }

    // Compare each element for equality.
    for (let i = 0, n = a.length; i < n; ++i) {
      if (fn ? !fn(a[i], b[i]) : a[i] !== b[i]) {
        return false;
      }
    }

    // The array are shallowly equal.
    return true;
  }

  /**
   * Create a slice of an array subject to an optional step.
   *
   * @param array - The array-like object of interest.
   *
   * @param options - The options for configuring the slice.
   *
   * @returns A new array with the specified values.
   *
   * @throws An exception if the slice `step` is `0`.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * A `start`, `stop`, or `step` which is non-integral.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let data = [0, 3, 4, 7, 7, 9];
   * ArrayExt.slice(data);                         // [0, 3, 4, 7, 7, 9]
   * ArrayExt.slice(data, { start: 2 });           // [4, 7, 7, 9]
   * ArrayExt.slice(data, { start: 0, stop: 4 });  // [0, 3, 4, 7]
   * ArrayExt.slice(data, { step: 2 });            // [0, 4, 7]
   * ArrayExt.slice(data, { step: -1 });           // [9, 7, 7, 4, 3, 0]
   * ```
   */
  export
  function slice<T>(array: ArrayLike<T>, options: slice.IOptions = {}): T[] {
    // Extract the options.
    let { start, stop, step } = options;

    // Set up the `step` value.
    if (step === undefined) {
      step = 1;
    }

    // Validate the step size.
    if (step === 0) {
      throw new Error('Slice `step` cannot be zero.');
    }

    // Look up the length of the array.
    let n = array.length;

    // Set up the `start` value.
    if (start === undefined) {
      start = step < 0 ? n - 1 : 0;
    } else if (start < 0) {
      start = Math.max(start + n, step < 0 ? -1 : 0);
    } else if (start >= n) {
      start = step < 0 ? n - 1 : n;
    }

    // Set up the `stop` value.
    if (stop === undefined) {
      stop = step < 0 ? -1 : n;
    } else if (stop < 0) {
      stop = Math.max(stop + n, step < 0 ? -1 : 0);
    } else if (stop >= n) {
      stop = step < 0 ? n - 1 : n;
    }

    // Compute the slice length.
    let length;
    if ((step < 0 && stop >= start) || (step > 0 && start >= stop)) {
      length = 0;
    } else if (step < 0) {
      length = Math.floor((stop - start + 1) / step + 1);
    } else {
      length = Math.floor((stop - start - 1) / step + 1);
    }

    // Compute the sliced result.
    let result: T[] = [];
    for (let i = 0; i < length; ++i) {
      result[i] = array[start + i * step];
    }

    // Return the result.
    return result;
  }

  /**
   * The namespace for the `slice` function statics.
   */
  export
  namespace slice {
    /**
     * The options for the `slice` function.
     */
    export
    interface IOptions {
      /**
       * The starting index of the slice, inclusive.
       *
       * Negative values are taken as an offset from the end
       * of the array.
       *
       * The default is `0` if `step > 0` else `n - 1`.
       */
      start?: number;

      /**
       * The stopping index of the slice, exclusive.
       *
       * Negative values are taken as an offset from the end
       * of the array.
       *
       * The default is `n` if `step > 0` else `-n - 1`.
       */
      stop?: number;

      /**
       * The step value for the slice.
       *
       * This must not be `0`.
       *
       * The default is `1`.
       */
      step?: number;
    }
  }

  /**
   * An array-like object which supports item assignment.
   */
  export
  type MutableArrayLike<T> = {
    readonly length: number;
    [index: number]: T;
  };

  /**
   * Move an element in an array from one index to another.
   *
   * @param array - The mutable array-like object of interest.
   *
   * @param fromIndex - The index of the element to move. Negative
   *   values are taken as an offset from the end of the array.
   *
   * @param toIndex - The target index of the element. Negative
   *   values are taken as an offset from the end of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * A `fromIndex` or `toIndex` which is non-integral.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from from '@phosphor/algorithm';
   *
   * let data = [0, 1, 2, 3, 4];
   * ArrayExt.move(data, 1, 2);  // [0, 2, 1, 3, 4]
   * ArrayExt.move(data, 4, 2);  // [0, 2, 4, 1, 3]
   * ```
   */
  export
  function move<T>(array: MutableArrayLike<T>, fromIndex: number, toIndex: number): void {
    let n = array.length;
    if (n <= 1) {
      return;
    }
    if (fromIndex < 0) {
      fromIndex = Math.max(0, fromIndex + n);
    } else {
      fromIndex = Math.min(fromIndex, n - 1);
    }
    if (toIndex < 0) {
      toIndex = Math.max(0, toIndex + n);
    } else {
      toIndex = Math.min(toIndex, n - 1);
    }
    if (fromIndex === toIndex) {
      return
    }
    let value = array[fromIndex];
    let d = fromIndex < toIndex ? 1 : -1;
    for (let i = fromIndex; i !== toIndex; i += d) {
      array[i] = array[i + d];
    }
    array[toIndex] = value;
  }

  /**
   * Reverse an array in-place.
   *
   * @param array - The mutable array-like object of interest.
   *
   * @param start - The index of the first element in the range to be
   *   reversed, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   reversed, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * A `start` or  `stop` index which is non-integral.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let data = [0, 1, 2, 3, 4];
   * ArrayExt.reverse(data, 1, 3);  // [0, 3, 2, 1, 4]
   * ArrayExt.reverse(data, 3);     // [0, 3, 2, 4, 1]
   * ArrayExt.reverse(data);        // [1, 4, 2, 3, 0]
   * ```
   */
  export
  function reverse<T>(array: MutableArrayLike<T>, start = 0, stop = -1): void {
    let n = array.length;
    if (n <= 1) {
      return;
    }
    if (start < 0) {
      start = Math.max(0, start + n);
    } else {
      start = Math.min(start, n - 1);
    }
    if (stop < 0) {
      stop = Math.max(0, stop + n);
    } else {
      stop = Math.min(stop, n - 1);
    }
    while (start < stop) {
      let a = array[start];
      let b = array[stop];
      array[start++] = b;
      array[stop--] = a;
    }
  }

  /**
   * Rotate the elements of an array in-place.
   *
   * @param array - The mutable array-like object of interest.
   *
   * @param delta - The amount of rotation to apply to the elements. A
   *   positive value will rotate the elements to the left. A negative
   *   value will rotate the elements to the right.
   *
   * @param start - The index of the first element in the range to be
   *   rotated, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   rotated, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * A `delta`, `start`, or `stop` which is non-integral.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let data = [0, 1, 2, 3, 4];
   * ArrayExt.rotate(data, 2);        // [2, 3, 4, 0, 1]
   * ArrayExt.rotate(data, -2);       // [0, 1, 2, 3, 4]
   * ArrayExt.rotate(data, 10);       // [0, 1, 2, 3, 4]
   * ArrayExt.rotate(data, 9);        // [4, 0, 1, 2, 3]
   * ArrayExt.rotate(data, 2, 1, 3);  // [4, 2, 0, 1, 3]
   * ```
   */
  export
  function rotate<T>(array: MutableArrayLike<T>, delta: number, start = 0, stop = -1): void {
    let n = array.length;
    if (n <= 1) {
      return;
    }
    if (start < 0) {
      start = Math.max(0, start + n);
    } else {
      start = Math.min(start, n - 1);
    }
    if (stop < 0) {
      stop = Math.max(0, stop + n);
    } else {
      stop = Math.min(stop, n - 1);
    }
    if (start >= stop) {
      return;
    }
    let length = stop - start + 1;
    if (delta > 0) {
      delta = delta % length;
    } else if (delta < 0) {
      delta = ((delta % length) + length) % length;
    }
    if (delta === 0) {
      return;
    }
    let pivot = start + delta;
    reverse(array, start, pivot - 1);
    reverse(array, pivot, stop);
    reverse(array, start, stop);
  }

  /**
   * Fill an array with a static value.
   *
   * @param array - The mutable array-like object to fill.
   *
   * @param value - The static value to use to fill the array.
   *
   * @param start - The index of the first element in the range to be
   *   filled, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   filled, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * #### Notes
   * If `stop < start` the fill will wrap at the end of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * A `start` or `stop` which is non-integral.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let data = ['one', 'two', 'three', 'four'];
   * ArrayExt.fill(data, 'r');        // ['r', 'r', 'r', 'r']
   * ArrayExt.fill(data, 'g', 1);     // ['r', 'g', 'g', 'g']
   * ArrayExt.fill(data, 'b', 2, 3);  // ['r', 'g', 'b', 'b']
   * ArrayExt.fill(data, 'z', 3, 1);  // ['z', 'z', 'b', 'z']
   * ```
   */
  export
  function fill<T>(array: MutableArrayLike<T>, value: T, start = 0, stop = -1): void {
    let n = array.length;
    if (n === 0) {
      return;
    }
    if (start < 0) {
      start = Math.max(0, start + n);
    } else {
      start = Math.min(start, n - 1);
    }
    if (stop < 0) {
      stop = Math.max(0, stop + n);
    } else {
      stop = Math.min(stop, n - 1);
    }
    let span: number;
    if (stop < start) {
      span = (stop + 1) + (n - start);
    } else {
      span = stop - start + 1;
    }
    for (let i = 0; i < span; ++i) {
      array[(start + i) % n] = value;
    }
  }

  /**
   * Insert a value into an array at a specific index.
   *
   * @param array - The array of interest.
   *
   * @param index - The index at which to insert the value. Negative
   *   values are taken as an offset from the end of the array.
   *
   * @param value - The value to set at the specified index.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * An `index` which is non-integral.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let data = [0, 1, 2];
   * ArrayExt.insert(data, 0, -1);  // [-1, 0, 1, 2]
   * ArrayExt.insert(data, 2, 12);  // [-1, 0, 12, 1, 2]
   * ArrayExt.insert(data, -1, 7);  // [-1, 0, 12, 1, 7, 2]
   * ArrayExt.insert(data, 6, 19);  // [-1, 0, 12, 1, 7, 2, 19]
   * ```
   */
  export
  function insert<T>(array: Array<T>, index: number, value: T): void {
    let n = array.length;
    if (index < 0) {
      index = Math.max(0, index + n);
    } else {
      index = Math.min(index, n);
    }
    for (let i = n; i > index; --i) {
      array[i] = array[i - 1];
    }
    array[index] = value;
  }

  /**
   * Remove and return a value at a specific index in an array.
   *
   * @param array - The array of interest.
   *
   * @param index - The index of the value to remove. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The value at the specified index, or `undefined` if the
   *   index is out of range.
   *
   * #### Complexity
   * Linear.
   *
   * #### Undefined Behavior
   * An `index` which is non-integral.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let data = [0, 12, 23, 39, 14, 12, 75];
   * ArrayExt.removeAt(data, 2);   // 23
   * ArrayExt.removeAt(data, -2);  // 12
   * ArrayExt.removeAt(data, 10);  // undefined;
   * ```
   */
  export
  function removeAt<T>(array: Array<T>, index: number): T | undefined {
    let n = array.length;
    if (index < 0) {
      index += n;
    }
    if (index < 0 || index >= n) {
      return undefined;
    }
    let value = array[index];
    for (let i = index + 1; i < n; ++i) {
      array[i - 1] = array[i];
    }
    array.length = n - 1;
    return value;
  }

  /**
   * Remove the first occurrence of a value from an array.
   *
   * @param array - The array of interest.
   *
   * @param value - The value to remove from the array. Values are
   *   compared using strict `===` equality.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The index of the removed value, or `-1` if the value
   *   is not contained in the array.
   *
   * #### Notes
   * If `stop < start` the search will wrap at the end of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let data = [0, 12, 23, 39, 14, 12, 75];
   * ArrayExt.removeFirstOf(data, 12);        // 1
   * ArrayExt.removeFirstOf(data, 17);        // -1
   * ArrayExt.removeFirstOf(data, 39, 3);     // -1
   * ArrayExt.removeFirstOf(data, 39, 3, 2);  // 2
   * ```
   */
  export
  function removeFirstOf<T>(array: Array<T>, value: T, start = 0, stop = -1): number {
    let index = firstIndexOf(array, value, start, stop);
    if (index !== -1) {
      removeAt(array, index);
    }
    return index;
  }

  /**
   * Remove the last occurrence of a value from an array.
   *
   * @param array - The array of interest.
   *
   * @param value - The value to remove from the array. Values are
   *   compared using strict `===` equality.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The index of the removed value, or `-1` if the value
   *   is not contained in the array.
   *
   * #### Notes
   * If `start < stop` the search will wrap at the end of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let data = [0, 12, 23, 39, 14, 12, 75];
   * ArrayExt.removeLastOf(data, 12);        // 5
   * ArrayExt.removeLastOf(data, 17);        // -1
   * ArrayExt.removeLastOf(data, 39, 2);     // -1
   * ArrayExt.removeLastOf(data, 39, 2, 3);  // 3
   * ```
   */
  export
  function removeLastOf<T>(array: Array<T>, value: T, start = -1, stop = 0): number {
    let index = lastIndexOf(array, value, start, stop);
    if (index !== -1) {
      removeAt(array, index);
    }
    return index;
  }

  /**
   * Remove all occurrences of a value from an array.
   *
   * @param array - The array of interest.
   *
   * @param value - The value to remove from the array. Values are
   *   compared using strict `===` equality.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The number of elements removed from the array.
   *
   * #### Notes
   * If `stop < start` the search will conceptually wrap at the end of
   * the array, however the array will be traversed front-to-back.
   *
   * #### Complexity
   * Linear.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * let data = [14, 12, 23, 39, 14, 12, 19, 14];
   * ArrayExt.removeAllOf(data, 12);        // 2
   * ArrayExt.removeAllOf(data, 17);        // 0
   * ArrayExt.removeAllOf(data, 14, 1, 4);  // 1
   * ```
   */
  export
  function removeAllOf<T>(array: Array<T>, value: T, start = 0, stop = -1): number {
    let n = array.length;
    if (n === 0) {
      return 0;
    }
    if (start < 0) {
      start = Math.max(0, start + n);
    } else {
      start = Math.min(start, n - 1);
    }
    if (stop < 0) {
      stop = Math.max(0, stop + n);
    } else {
      stop = Math.min(stop, n - 1);
    }
    let count = 0;
    for (let i = 0; i < n; ++i) {
      if (start <= stop && (i >= start && i <= stop) && array[i] === value) {
        count++;
      } else if (stop < start && (i <= stop || i >= start) && array[i] === value) {
        count++;
      } else if (count > 0) {
        array[i - count] = array[i];
      }
    }
    if (count > 0) {
      array.length = n - count;
    }
    return count;
  }

  /**
   * Remove the first occurrence of a value which matches a predicate.
   *
   * @param array - The array of interest.
   *
   * @param fn - The predicate function to apply to the values.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The removed `{ index, value }`, which will be `-1` and
   *   `undefined` if the value is not contained in the array.
   *
   * #### Notes
   * If `stop < start` the search will wrap at the end of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * function isEven(value: number): boolean {
   *   return value % 2 === 0;
   * }
   *
   * let data = [0, 12, 23, 39, 14, 12, 75];
   * ArrayExt.removeFirstWhere(data, isEven);     // { index: 0, value: 0 }
   * ArrayExt.removeFirstWhere(data, isEven, 2);  // { index: 3, value: 14 }
   * ArrayExt.removeFirstWhere(data, isEven, 4);  // { index: -1, value: undefined }
   * ```
   */
  export
  function removeFirstWhere<T>(array: Array<T>, fn: (value: T, index: number) => boolean, start = 0, stop = -1): { index: number, value: T | undefined } {
    let value: T | undefined;
    let index = findFirstIndex(array, fn, start, stop);
    if (index !== -1) {
      value = removeAt(array, index);
    }
    return { index, value };
  }

  /**
   * Remove the last occurrence of a value which matches a predicate.
   *
   * @param array - The array of interest.
   *
   * @param fn - The predicate function to apply to the values.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The removed `{ index, value }`, which will be `-1` and
   *   `undefined` if the value is not contained in the array.
   *
   * #### Notes
   * If `start < stop` the search will wrap at the end of the array.
   *
   * #### Complexity
   * Linear.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * function isEven(value: number): boolean {
   *   return value % 2 === 0;
   * }
   *
   * let data = [0, 12, 23, 39, 14, 12, 75];
   * ArrayExt.removeLastWhere(data, isEven);        // { index: 5, value: 12 }
   * ArrayExt.removeLastWhere(data, isEven, 2);     // { index: 1, value: 12 }
   * ArrayExt.removeLastWhere(data, isEven, 2, 1);  // { index: -1, value: undefined }
   * ```
   */
  export
  function removeLastWhere<T>(array: Array<T>, fn: (value: T, index: number) => boolean, start = -1, stop = 0): { index: number, value: T | undefined } {
    let value: T | undefined;
    let index = findLastIndex(array, fn, start, stop);
    if (index !== -1) {
      value = removeAt(array, index);
    }
    return { index, value };
  }

  /**
   * Remove all occurrences of values which match a predicate.
   *
   * @param array - The array of interest.
   *
   * @param fn - The predicate function to apply to the values.
   *
   * @param start - The index of the first element in the range to be
   *   searched, inclusive. The default value is `0`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @param stop - The index of the last element in the range to be
   *   searched, inclusive. The default value is `-1`. Negative values
   *   are taken as an offset from the end of the array.
   *
   * @returns The number of elements removed from the array.
   *
   * #### Notes
   * If `stop < start` the search will conceptually wrap at the end of
   * the array, however the array will be traversed front-to-back.
   *
   * #### Complexity
   * Linear.
   *
   * #### Example
   * ```typescript
   * import { ArrayExt } from '@phosphor/algorithm';
   *
   * function isEven(value: number): boolean {
   *   return value % 2 === 0;
   * }
   *
   * function isNegative(value: number): boolean {
   *   return value < 0;
   * }
   *
   * let data = [0, 12, -13, -9, 23, 39, 14, -15, 12, 75];
   * ArrayExt.removeAllWhere(data, isEven);            // 4
   * ArrayExt.removeAllWhere(data, isNegative, 0, 3);  // 2
   * ```
   */
  export
  function removeAllWhere<T>(array: Array<T>, fn: (value: T, index: number) => boolean, start = 0, stop = -1): number {
    let n = array.length;
    if (n === 0) {
      return 0;
    }
    if (start < 0) {
      start = Math.max(0, start + n);
    } else {
      start = Math.min(start, n - 1);
    }
    if (stop < 0) {
      stop = Math.max(0, stop + n);
    } else {
      stop = Math.min(stop, n - 1);
    }
    let count = 0;
    for (let i = 0; i < n; ++i) {
      if (start <= stop && (i >= start && i <= stop) && fn(array[i], i)) {
        count++;
      } else if (stop < start && (i <= stop || i >= start) && fn(array[i], i)) {
        count++;
      } else if (count > 0) {
        array[i - count] = array[i];
      }
    }
    if (count > 0) {
      array.length = n - count;
    }
    return count;
  }
}