🚀 go-pugleaf

"Dresse Alain" writes:
 > 
 > I have attempted to implement this with the code included below, but
 > I have the following unexpected result :
 > 
 > P({1}) * P({2});
 > 
 >                    -1
 > ==> - P({1})*P({1})  *P({2,1})
 > 
 > 
 > reval(ws);
 > 
 > ==> - P({2,1})
 > 
 > I have no idea why the result is not fully evaluated in the first
 > place.

The problem is that you are generating non-unique (i.e. non eq)
kernels by using the symbolic operator .** instead of calling mksp.
Hence, REDUCE is not able to cancel the two instances of P({1}) until
you feed them back into the simplifier by calling reval.

The following definition of simpp works:

symbolic procedure simpp u; 
   begin scalar a; 
      a := aeval car u; 
      if not listp a or car a neq 'list
        then return !*p2q mksp({'p, a},1);
      if null cdr a then return 1 ./ 1; 
      a := antisym_list cdr a; 
      if car a eq 0 then return nil ./ 1; 
      if car a eq 1 then return !*p2q mksp({'p, 'list . cdr a},1); 
      return !*t2q (mksp({'p, 'list . cdr a},1) .*  - 1)
   end;


   Rainer Schoepf
   Konrad-Zuse-Zentrum
    fuer Informationstechnik Berlin
   Heilbronner Strasse 10
   W-1000 Berlin 31
   Federal Republic of Germany
   <Schoepf@sc.ZIB-Berlin.de> or <Schoepf@sc.ZIB-Berlin.dbp.de>