/*           Bank Accounts!  

Using closures like in Scheme/Perl.  The difference being that these 
accounts are typed.

*/

public class topping
{

static (String,int)->void  makeaccount(int balance)
{  String name = "fred";

   (int)->void withdraw;
   withdraw = fun (int amt)->void 
     { balance = balance - amt; System.out.println(balance); };   
   (int)->void deposit;
   deposit = fun (int amt)->void 
     { balance = balance + amt; System.out.println(balance); };   
 
   (String,int)->void gateway;
   gateway = fun (String Op,int amt)->void 
     {  
          if (Op.equals("deposit")) deposit(amt);
            else if (Op.equals("withdraw")) withdraw(amt);
		else System.out.println("operation not allowed");
     
     };

    return gateway;
}  // end makeaccount

// another sample closure function, this time typed!
static ()->boolean makeflag(boolean value)
{  
   ()->boolean f;
   f = fun ()->boolean { value = !value;  return !value; };
   return f;
}

// myflag = makeflag(true);

// myflag()  == myflag()   -> false

public static void main(String[] args)
{

  (String,int)->void myaccount;
  (String,int)->void youraccount;

  myaccount = makeaccount(200);
  youraccount = makeaccount(300);
  myaccount("withdraw",30);
  youraccount("deposit",40);
  myaccount("withdraw",10); 

()->boolean f1 = makeflag(true);
()->boolean f2 = makeflag(false); // etc...
System.out.println(f1() == f1());
  

} // end main


} // end class topping