case OR: f=cform(a); f=f.or(cform(b)); return k2pos(f,x);
case IFF: f=cform(a); f=f.iff(cform(b)); return k2pos(f,x);
case PLUSPLUS: s=cset(a); return s.override(cset(b));
case MUL: i=cint(a); return i.multiply(cint(b));
case DIV: i=cint(a); return i.divide(cint(b));
case REM: i=cint(a); return i.modulo(cint(b));
case SHL: i=cint(a); return i.shl(cint(b));
case SHR: i=cint(a); return i.shr(cint(b));
case SHA: i=cint(a); return i.sha(cint(b));
case PLUS:
obj = visitThis(a);