mathjs/src/expression/transform/map.transform.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 maxArgumentCount = require('../../utils/function').maxArgumentCount
const map = require('../../utils/array').map

/**
 * Attach a transform function to math.map
 * Adds a property transform containing the transform function.
 *
 * This transform creates a one-based index instead of a zero-based index
 */
function factory (type, config, load, typed) {
  const compileInlineExpression = load(require('./utils/compileInlineExpression'))
  const matrix = load(require('../../type/matrix/function/matrix'))

  function mapTransform (args, math, scope) {
    let x, callback

    if (args[0]) {
      x = args[0].compile().eval(scope)
    }

    if (args[1]) {
      if (type.isSymbolNode(args[1]) || type.isFunctionAssignmentNode(args[1])) {
        // a function pointer, like filter([3, -2, 5], myTestFunction)
        callback = args[1].compile().eval(scope)
      } else {
        // an expression like filter([3, -2, 5], x > 0)
        callback = compileInlineExpression(args[1], math, scope)
      }
    }

    return map(x, callback)
  }
  mapTransform.rawArgs = true

  // one-based version of map function
  let map = typed('map', {
    'Array, function': function (x, callback) {
      return _map(x, callback, x)
    },

    'Matrix, function': function (x, callback) {
      return matrix(_map(x.valueOf(), callback, x))
    }
  })

  return mapTransform
}

/**
 * Map for a multi dimensional array. One-based indexes
 * @param {Array} array
 * @param {function} callback
 * @param {Array} orig
 * @return {Array}
 * @private
 */
function _map (array, callback, orig) {
  // figure out what number of arguments the callback function expects
  const argsCount = maxArgumentCount(callback)

  function recurse (value, index) {
    if (Array.isArray(value)) {
      return map(value, function (child, i) {
        // we create a copy of the index array and append the new index value
        return recurse(child, index.concat(i + 1)) // one based index, hence i + 1
      })
    } else {
      // invoke the (typed) callback function with the right number of arguments
      if (argsCount === 1) {
        return callback(value)
      } else if (argsCount === 2) {
        return callback(value, index)
      } else { // 3 or -1
        return callback(value, index, orig)
      }
    }
  }

  return recurse(array, [])
}

exports.name = 'map'
exports.path = 'expression.transform'
exports.factory = factory