anchor.diff:  [] value [all-pass]      ( private ) // ( -- ["words"] ) array of words for all-pass in selftest
   : ***           ( <description> -- ) // Start a selftest section
                   CR word trim ( desc )
  -                \ <js> "*** " + pop() + " ... " </jsV> to description
                   s" *** {} ... " :> format(pop()) to description
                   depth if 
                       description . ." aborted" cr 
  
positive.code:                 compiling if ( n word ) 
                      char getattr(vm,"{}")["{}"]=pop() 
                      :> format(tos().vid,pop().name) ( n s ) 
                      dup comment , compyle , ( n ) \ n has already been compiled as a literal
                  else ( n word )
                      py: getattr(vm,tos().vid)[pop().name]=pop(1)
                  then ; immediate
  
negative.code:     BL word (create) 
  <py> 
  last().type = "constant";
  source = '\tpush(getattr(vm,"{}")["{}"])'.format(current, last().name)
  last().xt = genxt('constant',source)
  if not getattr(vm,current,False): setattr(vm,current,{})
  exec('getattr(vm,"{}")["{}"]=pop()'.format(current, last().name))
  </py> reveal ; 
  