anchor.diff:  */
   grammar R;
   
  -prog:   (   expr (';'|NL)
  +prog:   (   expr (';'|NL)*
           |   NL
           )*
           EOF
  
positive.code: form:   ID
      |   ID '=' expr
      |   '...'
      ;
  
  sublist : sub (',' sub)* ;
  
negative.code:     |   'NULL' '='
      |   'NULL' '=' expr
      |   '...'
      |   '.'
      |
      ;
  
  