function Queue(){
this.queue=[];}


Queue.prototype.push_tail=function(msg){
this.queue.reverse();
this.queue.push(msg);
this.queue.reverse();};


Queue.prototype.push_head=function(msg){
this.queue.push(msg);};


Queue.prototype.pop=function(){
return this.queue.pop();};


Queue.prototype.is_empty=function(){
return this.queue.length==0;};


var current_process;
var process_queue=new Queue();
var pid_count=0;

function Process(thunk){
var p=this;
p.pid=++pid_count;
p.cont=function(){current_process=p;thunk();current_process=undefined;};
p.mailbox=new Queue();
p.blocked=false;}




function send(process,msg){var njf0 = njen(this,arguments,"process","msg");nj:while(1) { switch(njf0.cp) { case 0:
if(njf0._process.blocked){
njf0._process.blocked=false;
schedule(njf0._process);}


njf0._process.mailbox.push_tail(njf0._msg);njf0.cp = 1;
concede(njf0);return;case 1:break nj; }} njex(njf0);}


function block_if_no_messages(k){
if(current_process.mailbox.is_empty()){
var p=current_process;
p.blocked=true;
p.cont=function(){current_process=p;k();current_process=undefined;};
next_process();}}



function receive(){var njf0 = njen(this,arguments);nj:while(1) { switch(njf0.cp) { case 0:njf0.cp = 1;
block_if_no_messages(njf0);return;case 1:
njf0._msg=current_process.mailbox.pop();njex(njf0,
njf0._msg);return;break nj; }} njex(njf0);}


function schedule(process){
process_queue.push_tail(process);
start_scheduler();}


function unschedule(){
return process_queue.pop();}


function concede(k){
var p=current_process;
p.cont=function(){current_process=p;k();current_process=undefined;};
schedule(p);
next_process();}



function sleep(ms,cont){var njf0 = njen(this,arguments,"ms","cont");nj:while(1) { switch(njf0.cp) { case 0:
njf0._s=10;case 1:
njf0.cp = (njf0._s<njf0._ms) ? 2 : 3; break;case 2:njf0.cp = 4;
concede(njf0);return;case 4:
njf0._s+=10;njf0.cp=1; break;case 3:break nj; }} njex(njf0);}



function start(processes){
for(var i=0;i<processes.length;++i){
process_queue.push_head(processes[i]);}

start_scheduler();}


function spawn(func){
var p=new Process(func);
start([p]);
return p;}


var scheduler_started=false;

function start_scheduler(){
if(!scheduler_started){
scheduler_started=true;
while(!process_queue.is_empty()){
next_process();}}


scheduler_started=false;}


function next_process(){
var p=unschedule();
if(p){
var k=p.cont;
if(k){
setTimeout(k,10);}}}