mathjs/lib/expression/node/Node.js

'use strict';

var keywords = require('../keywords');

function factory (type, config, load, typed) {
  /**
   * Node
   */
  function Node() {
    if (!(this instanceof Node)) {
      throw new SyntaxError('Constructor must be called with the new operator');
    }
  }

  /**
   * Evaluate the node
   * @return {*} result
   */
    // TODO: cleanup deprecated code one day. Deprecated since version 0.19.0
  Node.prototype.eval = function () {
    throw new Error('Node.eval is deprecated. ' +
        'Use Node.compile(math).eval([scope]) instead.');
  };

  Node.prototype.type = 'Node';

  Node.prototype.isNode = true;

  /**
   * Compile the node to javascript code
   * @param {Object} math             math.js instance
   * @return {{eval: function}} expr  Returns an object with a function 'eval',
   *                                  which can be invoked as expr.eval([scope]),
   *                                  where scope is an optional object with
   *                                  variables.
   */
  Node.prototype.compile = function (math) {
    if (!(math instanceof Object)) {
      throw new TypeError('Object expected for parameter math');
    }

    // definitions globally available inside the closure of the compiled expressions
    var defs = {
      math: _transform(math),
      args: {}, // can be filled with names of FunctionAssignment arguments
      _validateScope: _validateScope
    };

    var code = this._compile(defs);

    var defsCode = Object.keys(defs).map(function (name) {
      return '    var ' + name + ' = defs["' + name + '"];';
    });

    var factoryCode =
        defsCode.join(' ') +
        'return {' +
        '  "eval": function (scope) {' +
        '    if (scope) _validateScope(scope);' +
        '    scope = scope || {};' +
        '    return ' + code + ';' +
        '  }' +
        '};';

    var factory = new Function('defs', factoryCode);
    return factory(defs);
  };

  /**
   * Compile the node to javascript code
   * @param {Object} defs     Object which can be used to define functions
   *                          and constants globally available inside the closure
   *                          of the compiled expression
   * @return {String} js
   * @private
   */
  Node.prototype._compile = function (defs) {
    // must be implemented by each of the Node implementations
    throw new Error('Cannot compile a Node interface');
  };

  /**
   * Execute a callback for each of the child nodes of this node
   * @param {function(child: Node, path: string, parent: Node)} callback
   */
  Node.prototype.forEach = function (callback) {
    // must be implemented by each of the Node implementations
    throw new Error('Cannot run forEach on a Node interface');
  };

  /**
   * Create a new Node having it's childs be the results of calling
   * the provided callback function for each of the childs of the original node.
   * @param {function(child: Node, path: string, parent: Node): Node} callback
   * @returns {OperatorNode} Returns a transformed copy of the node
   */
  Node.prototype.map = function (callback) {
    // must be implemented by each of the Node implementations
    throw new Error('Cannot run map on a Node interface');
  };

  /**
   * Validate whether an object is a Node, for use with map
   * @param {Node} node
   * @returns {Node} Returns the input if it's a node, else throws an Error
   * @protected
   */
  Node.prototype._ifNode = function (node) {
    if (!(node && node.isNode)) {
      throw new TypeError('Callback function must return a Node');
    }

    return node;
  };

  /**
   * Recursively traverse all nodes in a node tree. Executes given callback for
   * this node and each of its child nodes.
   * @param {function(node: Node, path: string, parent: Node)} callback
   *          A callback called for every node in the node tree.
   */
  Node.prototype.traverse = function (callback) {
    // execute callback for itself
    callback(this, null, null);

    // recursively traverse over all childs of a node
    function _traverse(node, callback) {
      node.forEach(function (child, path, parent) {
        callback(child, path, parent);
        _traverse(child, callback);
      });
    }

    _traverse(this, callback);
  };

  /**
   * Recursively transform a node tree via a transform function.
   *
   * For example, to replace all nodes of type SymbolNode having name 'x' with a
   * ConstantNode with value 2:
   *
   *     var res = Node.transform(function (node, path, parent) {
   *       if (node && node.isSymbolNode) && (node.name == 'x')) {
   *         return new ConstantNode(2);
   *       }
   *       else {
   *         return node;
   *       }
   *     });
   *
   * @param {function(node: Node, path: string, parent: Node) : Node} callback
   *          A mapping function accepting a node, and returning
   *          a replacement for the node or the original node.
   *          Signature: callback(node: Node, index: string, parent: Node) : Node
   * @return {Node} Returns the original node or its replacement
   */
  Node.prototype.transform = function (callback) {
    // check itself
    var replacement = callback(this, null, null);
    if (replacement !== this) {
      return replacement;
    }

    // traverse over all childs
    function _transform(node, callback) {
      return node.map(function (child, path, parent) {
        var replacement = callback(child, path, parent);
        return (replacement !== child) ? replacement : _transform(child, callback);
      });
    }

    return _transform(this, callback);
  };

  /**
   * Find any node in the node tree matching given filter function. For example, to
   * find all nodes of type SymbolNode having name 'x':
   *
   *     var results = Node.filter(function (node) {
   *       return (node && node.isSymbolNode) && (node.name == 'x');
   *     });
   *
   * @param {function(node: Node, path: string, parent: Node) : Node} callback
   *            A test function returning true when a node matches, and false
   *            otherwise. Function signature:
   *            callback(node: Node, index: string, parent: Node) : boolean
   * @return {Node[]} nodes       An array with nodes matching given filter criteria
   */
  Node.prototype.filter = function (callback) {
    var nodes = [];

    this.traverse(function (node, path, parent) {
      if (callback(node, path, parent)) {
        nodes.push(node);
      }
    });

    return nodes;
  };

  // TODO: deprecated since version 1.1.0, remove this some day
  Node.prototype.find = function () {
    throw new Error('Function Node.find is deprecated. Use Node.filter instead.');
  };

  // TODO: deprecated since version 1.1.0, remove this some day
  Node.prototype.match = function () {
    throw new Error('Function Node.match is deprecated. See functions Node.filter, Node.transform, Node.traverse.');
  };

  /**
   * Create a clone of this node, a shallow copy
   * @return {Node}
   */
  Node.prototype.clone = function () {
    // must be implemented by each of the Node implementations
    throw new Error('Cannot clone a Node interface');
  };

  /**
   * Get string representation
   * @return {String}
   */
  Node.prototype.toString = function () {
    return '';
  };

  /**
   * Get LaTeX representation. (wrapper function)
   * This functions get's either an object containing callbacks or
   * a single callback. It decides whether to call the callback and if
   * not or if the callback returns nothing, it calls the default
   * LaTeX implementation of the node (_toTex).
   *
   * @param {Object|function} callback(s)
   * @return {String}
   */
  Node.prototype.toTex = function (callback) {
    var customTex;
    if (typeof callback === 'object') {
      if ((this.type === 'FunctionNode') && callback.hasOwnProperty(this.name)) {
        //if callback is a map of callback functions and this is a FunctionNode
        customTex = callback[this.name](this, callback);
      }
    }
    else if (typeof callback === 'function') {
      //if callback is a function
      customTex = callback(this, callback);
    }
    else if (typeof callback !== 'undefined') {
      throw new TypeError('Object or function expected as callback');
    }

    if (typeof customTex !== 'undefined') {
      return customTex;
    }

    return this._toTex(callback);
  };

  /**
   * Internal function to generate the LaTeX output.
   * This has to be implemented by every Node
   *
   * @param {Object}|function}
   * @throws {Error}
   */
  Node.prototype._toTex = function () {
    if (this.type === 'Node') {
      //FIXME remove this in v2???
      return '';
    }
    //must be implemented by each of the Node implementations
    throw new Error('_toTex not implemented for ' + this.type);
  };

  /**
   * Get identifier.
   * @return {String}
   */
  Node.prototype.getIdentifier = function () {
    return this.type;
  };

  /**
   * Validate the symbol names of a scope.
   * Throws an error when the scope contains an illegal symbol.
   * @param {Object} scope
   */
  function _validateScope(scope) {
    for (var symbol in scope) {
      if (scope.hasOwnProperty(symbol)) {
        if (symbol in keywords) {
          throw new Error('Scope contains an illegal symbol, "' + symbol + '" is a reserved keyword');
        }
      }
    }
  }

  /**
   * Replace all functions having a transform function attached at property transform
   * with their transform.
   * @param {Object} math
   * @return {Object} transformed
   * @private
   */
  function _transform(math) {
    var transformed = Object.create(math);

    // TODO: bind function or function transform at compile time in FunctionNode instead, use defs there
    for (var name in math) {
      if (math.hasOwnProperty(name)) {
        var value = math[name];
        if (value && typeof value.transform === 'function') {
          transformed[name] = value.transform;
        }
      }
    }

    return transformed;
  }

  return Node;
}

exports.name = 'Node';
exports.path = 'expression.node';
exports.factory = factory;