mathjs/src/type/matrix/MatrixIndex.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 clone = require('../../utils/object').clone
const isInteger = require('../../utils/number').isInteger

function factory (type) {
  /**
   * Create an index. An Index can store ranges and sets for multiple dimensions.
   * Matrix.get, Matrix.set, and math.subset accept an Index as input.
   *
   * Usage:
   *     const index = new Index(range1, range2, matrix1, array1, ...)
   *
   * Where each parameter can be any of:
   *     A number
   *     A string (containing a name of an object property)
   *     An instance of Range
   *     An Array with the Set values
   *     A Matrix with the Set values
   *
   * The parameters start, end, and step must be integer numbers.
   *
   * @class Index
   * @Constructor Index
   * @param {...*} ranges
   */
  function Index (ranges) {
    if (!(this instanceof Index)) {
      throw new SyntaxError('Constructor must be called with the new operator')
    }

    this._dimensions = []
    this._isScalar = true

    for (let i = 0, ii = arguments.length; i < ii; i++) {
      const arg = arguments[i]

      if (type.isRange(arg)) {
        this._dimensions.push(arg)
        this._isScalar = false
      } else if (Array.isArray(arg) || type.isMatrix(arg)) {
        // create matrix
        const m = _createImmutableMatrix(arg.valueOf())
        this._dimensions.push(m)
        // size
        const size = m.size()
        // scalar
        if (size.length !== 1 || size[0] !== 1) {
          this._isScalar = false
        }
      } else if (typeof arg === 'number') {
        this._dimensions.push(_createImmutableMatrix([arg]))
      } else if (typeof arg === 'string') {
        // object property (arguments.count should be 1)
        this._dimensions.push(arg)
      } else {
        throw new TypeError('Dimension must be an Array, Matrix, number, string, or Range')
      }
      // TODO: implement support for wildcard '*'
    }
  }

  /**
   * Attach type information
   */
  Index.prototype.type = 'Index'
  Index.prototype.isIndex = true

  function _createImmutableMatrix (arg) {
    // loop array elements
    for (let i = 0, l = arg.length; i < l; i++) {
      if (typeof arg[i] !== 'number' || !isInteger(arg[i])) {
        throw new TypeError('Index parameters must be positive integer numbers')
      }
    }
    // create matrix
    return new type.ImmutableDenseMatrix(arg)
  }

  /**
   * Create a clone of the index
   * @memberof Index
   * @return {Index} clone
   */
  Index.prototype.clone = function () {
    const index = new Index()
    index._dimensions = clone(this._dimensions)
    index._isScalar = this._isScalar
    return index
  }

  /**
   * Create an index from an array with ranges/numbers
   * @memberof Index
   * @param {Array.<Array | number>} ranges
   * @return {Index} index
   * @private
   */
  Index.create = function (ranges) {
    const index = new Index()
    Index.apply(index, ranges)
    return index
  }

  /**
   * Retrieve the size of the index, the number of elements for each dimension.
   * @memberof Index
   * @returns {number[]} size
   */
  Index.prototype.size = function () {
    const size = []

    for (let i = 0, ii = this._dimensions.length; i < ii; i++) {
      const d = this._dimensions[i]
      size[i] = (typeof d === 'string') ? 1 : d.size()[0]
    }

    return size
  }

  /**
   * Get the maximum value for each of the indexes ranges.
   * @memberof Index
   * @returns {number[]} max
   */
  Index.prototype.max = function () {
    const values = []

    for (let i = 0, ii = this._dimensions.length; i < ii; i++) {
      const range = this._dimensions[i]
      values[i] = (typeof range === 'string') ? range : range.max()
    }

    return values
  }

  /**
   * Get the minimum value for each of the indexes ranges.
   * @memberof Index
   * @returns {number[]} min
   */
  Index.prototype.min = function () {
    const values = []

    for (let i = 0, ii = this._dimensions.length; i < ii; i++) {
      const range = this._dimensions[i]
      values[i] = (typeof range === 'string') ? range : range.min()
    }

    return values
  }

  /**
   * Loop over each of the ranges of the index
   * @memberof Index
   * @param {Function} callback   Called for each range with a Range as first
   *                              argument, the dimension as second, and the
   *                              index object as third.
   */
  Index.prototype.forEach = function (callback) {
    for (let i = 0, ii = this._dimensions.length; i < ii; i++) {
      callback(this._dimensions[i], i, this)
    }
  }

  /**
   * Retrieve the dimension for the given index
   * @memberof Index
   * @param {Number} dim                  Number of the dimension
   * @returns {Range | null} range
   */
  Index.prototype.dimension = function (dim) {
    return this._dimensions[dim] || null
  }

  /**
   * Test whether this index contains an object property
   * @returns {boolean} Returns true if the index is an object property
   */
  Index.prototype.isObjectProperty = function () {
    return this._dimensions.length === 1 && typeof this._dimensions[0] === 'string'
  }

  /**
   * Returns the object property name when the Index holds a single object property,
   * else returns null
   * @returns {string | null}
   */
  Index.prototype.getObjectProperty = function () {
    return this.isObjectProperty() ? this._dimensions[0] : null
  }

  /**
   * Test whether this index contains only a single value.
   *
   * This is the case when the index is created with only scalar values as ranges,
   * not for ranges resolving into a single value.
   * @memberof Index
   * @return {boolean} isScalar
   */
  Index.prototype.isScalar = function () {
    return this._isScalar
  }

  /**
   * Expand the Index into an array.
   * For example new Index([0,3], [2,7]) returns [[0,1,2], [2,3,4,5,6]]
   * @memberof Index
   * @returns {Array} array
   */
  Index.prototype.toArray = function () {
    const array = []
    for (let i = 0, ii = this._dimensions.length; i < ii; i++) {
      const dimension = this._dimensions[i]
      array.push((typeof dimension === 'string') ? dimension : dimension.toArray())
    }
    return array
  }

  /**
   * Get the primitive value of the Index, a two dimensional array.
   * Equivalent to Index.toArray().
   * @memberof Index
   * @returns {Array} array
   */
  Index.prototype.valueOf = Index.prototype.toArray

  /**
   * Get the string representation of the index, for example '[2:6]' or '[0:2:10, 4:7, [1,2,3]]'
   * @memberof Index
   * @returns {String} str
   */
  Index.prototype.toString = function () {
    const strings = []

    for (let i = 0, ii = this._dimensions.length; i < ii; i++) {
      const dimension = this._dimensions[i]
      if (typeof dimension === 'string') {
        strings.push(JSON.stringify(dimension))
      } else {
        strings.push(dimension.toString())
      }
    }

    return '[' + strings.join(', ') + ']'
  }

  /**
   * Get a JSON representation of the Index
   * @memberof Index
   * @returns {Object} Returns a JSON object structured as:
   *                   `{"mathjs": "Index", "ranges": [{"mathjs": "Range", start: 0, end: 10, step:1}, ...]}`
   */
  Index.prototype.toJSON = function () {
    return {
      mathjs: 'Index',
      dimensions: this._dimensions
    }
  }

  /**
   * Instantiate an Index from a JSON object
   * @memberof Index
   * @param {Object} json A JSON object structured as:
   *                     `{"mathjs": "Index", "dimensions": [{"mathjs": "Range", start: 0, end: 10, step:1}, ...]}`
   * @return {Index}
   */
  Index.fromJSON = function (json) {
    return Index.create(json.dimensions)
  }

  return Index
}

exports.name = 'Index'
exports.path = 'type'
exports.factory = factory