anchor.diff:     ;
   
   mathsymbol
  -   : (PRINTABLECHARACTER | LPAREN | RPAREN)+
  +   : (printablecharacter | LPAREN | RPAREN)+
  +   ;
  +
  +printablecharacter
  +   : PRINTABLECHARACTER | LABEL
      ;
   
   filename
  
positive.code: grammar metamath;
  
  database
     : outermostscopestmt*
     ;
  
  outermostscopestmt
  
negative.code:    : ')'
     ;
  
  LABEL
     : (LETTERORDIGIT | '.' | '-' | '_')+
     ;
  
  PRINTABLECHARACTER
     : [\u0021-\u007e]+
     ;
  
  fragment LETTERORDIGIT
  