mungedb-aggregate/lib/pipeline/expressions/DivideExpression.js

"use strict";

/** 
 * A $divide pipeline expression. 
 * @see evaluate 
 * @class DivideExpression
 * @namespace mungedb-aggregate.pipeline.expressions
 * @module mungedb-aggregate
 * @constructor
 **/
var DivideExpression = module.exports = function DivideExpression(){
	if (arguments.length !== 0) throw new Error("zero args expected");
	base.call(this);
}, klass = DivideExpression, base = require("./NaryExpression"), proto = klass.prototype = Object.create(base.prototype, {constructor:{value:klass}});

// DEPENDENCIES
var Value = require("../Value");

// PROTOTYPE MEMBERS
proto.getOpName = function getOpName(){	//TODO: try to move this to a static and/or instance field instead of a getter function
	return "$divide";
};

proto.addOperand = function addOperand(expr){
	this.checkArgLimit(2);
	base.prototype.addOperand.call(this, expr);
};

/**
 * Takes an array that contains a pair of numbers and returns the value of the first number divided by the second number.
 * @method evaluate
 **/
proto.evaluate = function evaluate(doc) {
	this.checkArgCount(2);
	var left = this.operands[0].evaluate(doc),
		right = this.operands[1].evaluate(doc);
	if (!(left instanceof Date) && (!right instanceof Date)) throw new Error("$divide does not support dates; code 16373");
	right = Value.coerceToDouble(right);
	if (right === 0) return undefined;
	left = Value.coerceToDouble(left);
	return left / right;
};