JavaScript (fake) continuations

call-cc3.js

var sys = require('sys');
  SLICE = Array.prototype.slice,
  STACK_EX = (function() {
    try {
      test();
    } catch(ex) {
      return ex.constructor;
    }
    
    throw "BUG";
    
    function test() {
      test();
    }
  })();

function Continuation(func, args) {
	this.func = func;
	this.args = args;
}

function NOW(func) {
  var args = SLICE.call(arguments, 1);
  try {
    func.apply(null, args);
  } catch (ex) {
    if (ex instanceof STACK_EX) {
      ex = new Continuation(func, args);
    }
    throw ex;
  }
}

function cps_call(func) {
  var cc = new Continuation(func, []);
  while (true) {
    try {
      cc.func.apply(null, cc.args);
      break;
    } catch (ex) {
      if (ex instanceof Continuation) {
        cc = ex;
      } else if (ex instanceof STACK_EX) {
        throw "BUG ???";
      } else {
        sys.puts(ex);
        throw ex;
      }
    }
  }
}

function sum(n, cont) {
    if (n == 0) NOW(cont, 0);
    NOW(sum, n - 1, function(result){
        NOW(cont, n + result);
    });
}

var i=100;
while(i--) {
cps_call(function(){
    // and what do you know, this time it works!
    // the result is 4501500
    sum(3000, function(result){
//        sys.puts(result);
    });
});
}