module fact. 
import obj.

type get    Value      -> o.           type g      int -> o.
type point o.  
type zero? o.       
type succ  o.
type pred  o.  
type intclass o.    
type writeobj Identifier ->  o.
  
(new intclass St Id || anti --> anti || object Id St Ms):-
  N = (M \ (pi S \ pi P \ pi Q \
                      (call Id pred || frozen Id S (P & Q) --> 
                       anti || object Id S (M & Q))
      )),
  Ms = (pi S \ pi M \ pi T \
        ( (write "ZERO!" >> 
             call Id zero? || frozen Id S M -->  anti || object Id S M)
        &
         (call Id succ  || frozen Id S    (M  & T)  --> 
                             anti || object Id S ((N M) & T))                
       )).

type factclass o.   type slave     o.
type receiver  o.   type eval      int -> o.
type st        int -> Identifier -> o. 
type fact      int -> Identifier -> o. 

(new slave St Id || anti --> anti || object Id St Ms):-
  Ms = (pi N \ pi N1 \ pi N2 \ pi Ms \ pi O \
         ((N2 is N1 * N) >>
              call Id (eval N1) || frozen Id (st N O) Ms --> 
                             send O  (eval N2) || anti)
        ).

(new factclass St Id || anti --> anti || object Id St Ms):-
  Ms = (pi S \ pi M \ pi N\ pi O\ pi T\ pi N1 \
          (((N =< 2) >>
                call Id (fact N O) || frozen Id S M --> 
                       send O  (eval N)   || object Id S M)
          &    
          ((N > 2, N1 is N - 1) >>
             call Id (fact N O) || frozen Id S M  --> 
               (pi id \(new slave (st N O) id | send Id (fact  N1 id))) 
                                                      || object Id S M
          ))).
       
(new receiver St Id || anti --> anti || object Id St Ms):-
  Ms = 
   (pi N \ pi S \ pi M \
       ((print "\n Result: ",write N,print "\n") >> 
           call Id (eval N) || frozen Id S M  --> anti || anti 
       )
   ).       

type stack o.  
type pop  Element  -> o.
type push Element -> o.
type a    list Element -> o.

(new stack St Id || anti --> 
         (anti || object Id (a nil) Ms)):-
 Ms = (pi S \ pi M \ pi El \
    ((call Id (pop El) || frozen Id (a (El::S)) M  --> 
                         anti || object Id (a S) M)
       & 
     (call Id (push El) || frozen Id (a S) M  --> 
                         anti || object Id (a (El::S)) M))).   
                        
initial anti.

type start o.
start:- spyon => 
    ehhfsolve ( new intclass anti 1 | 
                send 1 zero? | 
                send 1 succ | 
                send 1 pred | 
                send 1 zero?).
 
start:- 
    ehhfsolve ( new intclass anti 1 | 
               send 1 zero? | 
               send 1 succ | 
               send 1 pred | 
               send 1 zero?).
           
start:-
    ehhfsolve ( new intclass anti 1 | 
               send 1 zero? | 
               send 1 pred).
            
start:- spyon => 
    ehhfsolve ( new receiver  anti 1 | 
                new factclass anti 2 | 
                send 2 (fact 4 1)).

start:- ehhfsolve (new stack anti 1 | writeobj 1 | break 1 St).