mungedb-aggregate/lib/pipeline/accumulators/LastAccumulator.js

var LastAccumulator = module.exports = (function(){

	// Constructor
	/** 
	* Constructor for LastAccumulator, wraps SingleValueAccumulator's constructor and
	* finds the last document
	*
	* @class LastAccumulator
	* @namespace munge.pipeline.accumulators
	* @module munge
	* @constructor
	**/
	var klass = module.exports = function LastAccumulator(){
		base.call(this);
	}, SingleValueAccumulator = require("./SingleValueAccumulator"), base = SingleValueAccumulator, proto = klass.prototype = Object.create(base.prototype, {constructor:{value:klass}});

	proto.evaluate = function evaluate(doc){
		if(this.operands.length != 1) throw new Error("this should never happen");
		this.value = this.operands[0].evaluate(doc);
	};


	proto.getOpName = function getOpName(){
		return "$last";
	};

	return klass;

})();