anchor.diff:  
   bool_not_expression
    : comparison_expression
  - | NOT Right=bool_not_expression
  + | Op=NOT Right=bool_not_expression
    ;
   
   comparison_expression
  
positive.code:  | Real=FLOAT_NUMBER
   | Integer=( DECIMAL_INTEGER | OCT_INTEGER | HEX_INTEGER | BIN_INTEGER )
   | List=list_literal
  // | Tuple=tuple_literal
  // | Hash=hash_literal
   ;
  
  list_literal
   : '[' (First=bool_not_expression (',' Succession=bool_not_expression)* ','? )? ']'
   ;
  
  //tuple_literal
  // : '(' (expression ',' (expression ','?)* )? ')'
  // ;
  
  //hash_literal
  // : '{' (hash_element (',' hash_element)* ','? )? '}'
  // ;
  
  //hash_element
  // : expression ':' expression
  // ;
  
  /*
   * lexer rules
  
negative.code: 
  power_expression
   : // right-associative
     Left=unary_expression (Op=POWER Right=power_expression)?
   ;
  
  unary_expression
  