mathjs/lib/expression/node/FunctionAssignmentNode.js

'use strict';

var keywords = require('../keywords');
var escape = require('../../utils/string').escape;
var forEach = require('../../utils/array').forEach;
var join = require('../../utils/array').join;
var latex = require('../../utils/latex');
var operators = require('../operators');
var setSafeProperty = require('../../utils/customs').setSafeProperty;

function factory (type, config, load, typed) {
  var Node = load(require('./Node'));

  /**
   * @constructor FunctionAssignmentNode
   * @extends {Node}
   * Function assignment
   *
   * @param {string} name           Function name
   * @param {string[] | Array.<{name: string, type: string}>} params
   *                                Array with function parameter names, or an
   *                                array with objects containing the name
   *                                and type of the parameter
   * @param {Node} expr             The function expression
   */
  function FunctionAssignmentNode(name, params, expr) {
    if (!(this instanceof FunctionAssignmentNode)) {
      throw new SyntaxError('Constructor must be called with the new operator');
    }

    // validate input
    if (typeof name !== 'string') throw new TypeError('String expected for parameter "name"');
    if (!Array.isArray(params))  throw new TypeError('Array containing strings or objects expected for parameter "params"');
    if (!type.isNode(expr)) throw new TypeError('Node expected for parameter "expr"');
    if (name in keywords) throw new Error('Illegal function name, "' + name + '" is a reserved keyword');

    this.name = name;
    this.params = params.map(function (param) {
      return param && param.name || param;
    });
    this.types = params.map(function (param) {
      return param && param.type || 'any'
    });
    this.expr = expr;
  }

  FunctionAssignmentNode.prototype = new Node();

  FunctionAssignmentNode.prototype.type = 'FunctionAssignmentNode';

  FunctionAssignmentNode.prototype.isFunctionAssignmentNode = true;

  /**
   * Compile a node into a JavaScript function.
   * This basically pre-calculates as much as possible and only leaves open
   * calculations which depend on a dynamic scope with variables.
   * @param {Object} math     Math.js namespace with functions and constants.
   * @param {Object} argNames An object with argument names as key and `true`
   *                          as value. Used in the SymbolNode to optimize
   *                          for arguments from user assigned functions
   *                          (see FunctionAssignmentNode) or special symbols
   *                          like `end` (see IndexNode).
   * @return {function} Returns a function which can be called like:
   *                        evalNode(scope: Object, args: Object, context: *)
   */
  FunctionAssignmentNode.prototype._compile = function (math, argNames) {
    var childArgNames = Object.create(argNames);
    forEach(this.params, function (param) {
      childArgNames[param] = true;
    })

    // compile the function expression with the child args
    var evalExpr = this.expr._compile(math, childArgNames);
    var name = this.name;
    var params = this.params;
    var signature = join(this.types, ',');
    var syntax = name + '(' + join(this.params, ', ') + ')';

    return function evalFunctionAssignmentNode(scope, args, context) {
      var signatures = {}
      signatures[signature] = function () {
        var childArgs = Object.create(args);

        for (var i = 0; i < params.length; i++) {
          childArgs[params[i]] = arguments[i];
        }

        return evalExpr(scope, childArgs, context);
      }
      var fn = typed(name, signatures);
      fn.syntax = syntax;

      setSafeProperty(scope, name, fn);

      return fn;
    }
  }

  /**
   * Execute a callback for each of the child nodes of this node
   * @param {function(child: Node, path: string, parent: Node)} callback
   */
  FunctionAssignmentNode.prototype.forEach = function (callback) {
    callback(this.expr, 'expr', this);
  };

  /**
   * Create a new FunctionAssignmentNode 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 {FunctionAssignmentNode} Returns a transformed copy of the node
   */
  FunctionAssignmentNode.prototype.map = function (callback) {
    var expr = this._ifNode(callback(this.expr, 'expr', this));

    return new FunctionAssignmentNode(this.name, this.params.slice(0), expr);
  };

  /**
   * Create a clone of this node, a shallow copy
   * @return {FunctionAssignmentNode}
   */
  FunctionAssignmentNode.prototype.clone = function () {
    return new FunctionAssignmentNode(this.name, this.params.slice(0), this.expr);
  };

  /**
   * Is parenthesis needed?
   * @param {Node} node
   * @param {Object} parenthesis
   * @private
   */
  function needParenthesis(node, parenthesis) {
    var precedence = operators.getPrecedence(node, parenthesis);
    var exprPrecedence = operators.getPrecedence(node.expr, parenthesis);

    return (parenthesis === 'all')
      || ((exprPrecedence !== null) && (exprPrecedence <= precedence));
  }

  /**
   * get string representation
   * @param {Object} options
   * @return {string} str
   */
  FunctionAssignmentNode.prototype._toString = function (options) {
    var parenthesis = (options && options.parenthesis) ? options.parenthesis : 'keep';
    var expr = this.expr.toString(options);
    if (needParenthesis(this, parenthesis)) {
      expr = '(' + expr + ')';
    }
    return this.name + '(' + this.params.join(', ') + ') = ' + expr;
  };

  /**
   * get HTML representation
   * @param {Object} options
   * @return {string} str
   */
   FunctionAssignmentNode.prototype.toHTML = function (options) {
    var parenthesis = (options && options.parenthesis) ? options.parenthesis : 'keep';
	var params = [];
	for (var i=0; i<this.params.length; i++)	{
	  params.push('<span class="math-symbol math-parameter">' + escape(this.params[i]) + '</span>');
	}
    var expr = this.expr.toHTML(options);
    if (needParenthesis(this, parenthesis)) {
      expr = '<span class="math-parenthesis math-round-parenthesis">(</span>' + expr + '<span class="math-parenthesis math-round-parenthesis">)</span>';
    }
    return '<span class="math-function">' + escape(this.name) + '</span>' + '<span class="math-parenthesis math-round-parenthesis">(</span>' + params.join('<span class="math-separator">,</span>') + '<span class="math-parenthesis math-round-parenthesis">)</span><span class="math-operator math-assignment-operator math-variable-assignment-operator math-binary-operator">=</span>' + expr;
  };

  /**
   * get LaTeX representation
   * @param {Object} options
   * @return {string} str
   */
  FunctionAssignmentNode.prototype._toTex = function (options) {
    var parenthesis = (options && options.parenthesis) ? options.parenthesis : 'keep';
    var expr = this.expr.toTex(options);
    if (needParenthesis(this, parenthesis)) {
      expr = '\\left(' + expr + '\\right)';
    }

    return '\\mathrm{' + this.name
        + '}\\left(' + this.params.map(latex.toSymbol).join(',') + '\\right):=' + expr;
  };

  return FunctionAssignmentNode;
}
exports.name = 'FunctionAssignmentNode';
exports.path = 'expression.node';
exports.factory = factory;