mathjs/lib/function/set/setDistinct.js

'use strict';

var flatten = require('../../utils/array').flatten;

function factory(type, config, load, typed) {
  var MatrixIndex = load(require('../../type/matrix/MatrixIndex'));
  var DenseMatrix = load(require('../../type/matrix/DenseMatrix'));
  var size = load(require('../matrix/size'));
  var subset = load(require('../matrix/subset'));
  var compareNatural = load(require('../relational/compareNatural'));

  /**
   * Collect the distinct elements of a multiset.
   * A multi-dimension array will be converted to a single-dimension array before the operation.
   *
   * Syntax:
   *
   *    math.setDistinct(set)
   *
   * Examples:
   *
   *    math.setDistinct([1, 1, 1, 2, 2, 3])        // returns [1, 2, 3]
   *
   * See also:
   *
   *    setMultiplicity
   *
   * @param {Array | Matrix}    a  A multiset
   * @return {Array | Matrix}    A set containing the distinc elements of the multiset
   */
  var setDistinct = typed('setDistinct', {
    'Array | Matrix': function ArrayMatrix(a) {
      var result = void 0;
      if (subset(size(a), new MatrixIndex(0)) === 0) {
        // if empty, return empty
        result = [];
      } else {
        var b = flatten(Array.isArray(a) ? a : a.toArray()).sort(compareNatural);
        result = [];
        result.push(b[0]);
        for (var i = 1; i < b.length; i++) {
          if (compareNatural(b[i], b[i - 1]) !== 0) {
            result.push(b[i]);
          }
        }
      }
      // return an array, if the input was an array
      if (Array.isArray(a)) {
        return result;
      }
      // return a matrix otherwise
      return new DenseMatrix(result);
    }
  });

  return setDistinct;
}

exports.name = 'setDistinct';
exports.factory = factory;