mathjs/src/function/matrix/sort.js

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with dif

'use strict'

const size = require('../../utils/array').size

function factory (type, config, load, typed) {
  const matrix = load(require('../../type/matrix/function/matrix'))
  const compareAsc = load(require('../relational/compare'))
  const compareDesc = function (a, b) {
    return -compareAsc(a, b)
  }
  const compareNatural = load(require('../relational/compareNatural'))

  /**
   * Sort the items in a matrix.
   *
   * Syntax:
   *
   *    math.sort(x)
   *    math.sort(x, compare)
   *
   * Examples:
   *
   *    math.sort([5, 10, 1]) // returns [1, 5, 10]
   *    math.sort(['C', 'B', 'A', 'D'], math.compareNatural)
   *    // returns ['A', 'B', 'C', 'D']
   *
   *    function sortByLength (a, b) {
   *      return a.length - b.length
   *    }
   *    math.sort(['Langdon', 'Tom', 'Sara'], sortByLength)
   *    // returns ['Tom', 'Sara', 'Langdon']
   *
   * See also:
   *
   *    filter, forEach, map, compare, compareNatural
   *
   * @param {Matrix | Array} x    A one dimensional matrix or array to sort
   * @param {Function | 'asc' | 'desc' | 'natural'} [compare='asc']
   *        An optional _comparator function or name. The function is called as
   *        `compare(a, b)`, and must return 1 when a > b, -1 when a < b,
   *        and 0 when a == b.
   * @return {Matrix | Array} Returns the sorted matrix.
   */
  const sort = typed('sort', {
    'Array': function (x) {
      _arrayIsVector(x)
      return x.sort(compareAsc)
    },

    'Matrix': function (x) {
      _matrixIsVector(x)
      return matrix(x.toArray().sort(compareAsc), x.storage())
    },

    'Array, function': function (x, _comparator) {
      _arrayIsVector(x)
      return x.sort(_comparator)
    },

    'Matrix, function': function (x, _comparator) {
      _matrixIsVector(x)
      return matrix(x.toArray().sort(_comparator), x.storage())
    },

    'Array, string': function (x, order) {
      _arrayIsVector(x)
      return x.sort(_comparator(order))
    },

    'Matrix, string': function (x, order) {
      _matrixIsVector(x)
      return matrix(x.toArray().sort(_comparator(order)), x.storage())
    }
  })

  sort.toTex = undefined // use default template

  /**
   * Get the comparator for given order ('asc', 'desc', 'natural')
   * @param {'asc' | 'desc' | 'natural'} order
   * @return {Function} Returns a _comparator function
   */
  function _comparator (order) {
    if (order === 'asc') {
      return compareAsc
    } else if (order === 'desc') {
      return compareDesc
    } else if (order === 'natural') {
      return compareNatural
    } else {
      throw new Error('String "asc", "desc", or "natural" expected')
    }
  }

  /**
   * Validate whether an array is one dimensional
   * Throws an error when this is not the case
   * @param {Array} array
   * @private
   */
  function _arrayIsVector (array) {
    if (size(array).length !== 1) {
      throw new Error('One dimensional array expected')
    }
  }

  /**
   * Validate whether a matrix is one dimensional
   * Throws an error when this is not the case
   * @param {Matrix} matrix
   * @private
   */
  function _matrixIsVector (matrix) {
    if (matrix.size().length !== 1) {
      throw new Error('One dimensional matrix expected')
    }
  }

  return sort
}

exports.name = 'sort'
exports.factory = factory