anchor.diff:      String[] params = null;
   }
       : "def" name=qualifiableNames
  -      ((params=formalOpParameters equals) => params=formalOpParameters equals
  +      ((formalOpParameters equals) => params=formalOpParameters equals
          | equals) 
         expression
  +    ;
  +
  +private claimDefinition
  +{
  +    String name = null;
  +}
  +    : claimKind name=idName
  +      equals
  +      expression
  +    ;
  +
  +private claimKind
  +    : "theorem"
  +    | "axiom"
  +    | "conjecture"
       ;
   
   private expression
  
positive.code: 
  //---------------------------------------------------------------------------
  private definition
      : opDefinition;
  
  private opDefinition
  {
  
negative.code:        )*)?
        RPAREN                {params = (String[]) paramList.toArray(new String[]{});}
      ;
  
  //---------------------------------------------------------------------------
  private specialSymbol returns[String text]
  