//?EE?465?USC
//?Simulation?of?an?M/M/1?system

#include?
#include?
#include?
#include?

using?namespace?std;

#define?INFIN??			999999999

//?Function?Name:	expon
//?Description:?	Generates?an?exponentially?distributed?random?number?
//					with?parameter?\lambda.?
//?Input:?			lambda?（double）
//?Output:?			An?exponentially?distributed?random?number?（double）
//
double?expon（double?lambda）
{
	double?u;?//?used?to?store?a?random?number.?
	
	do
	{
		u?=?drand48（）;?//uniform?number?in?the?interval?[0.0?1.0]
	}
	while?（（u?==?0）?||?（u?==?1））;?//special?cases?that?we?want?to?avoid
	
	return?-log（1-u）/lambda;
	
}

//?Function?Name:	print_stats
//?Description:?	Saves?and?prints?system?statistics?
//?Input:???????????stats_file?（ostream?object）:?ostream?object?for?the?stats?file
//					avg_customers?（double）:?average?customers?in?the?system
//					avg_service_time?（double）:?average?service?time?
//?Output:?			void?（output?stored?to?file?and?printed?in?the?screen）
//
void?print_stats（ostream?&stats_file?double?avg_customers?double?avg_service_time）
{
	cout?<	cout?<	
	stats_file?<	stats_file?<}

//?The?main?function?of?the?program?that?is?called?at?the?beginning.
int?main（）?{
	//system?variables
	long?int?tot_arrivals?cur_arrivals?=?0;
	double?lambda?mu;
	double?event1?=?0.0?event2