anchor.diff:  dict -> '{' '}' :                #dict{line=?line('$1'), elements=[]}.
   dict -> '{' dict_entries '}' :   #dict{line=?line('$1'), elements='$2'}.
   
  -dict_entries -> range_expr '=>' expr : [{'$1','$3'}]. % FIXME: change add_expr to 1 below match
  -dict_entries -> range_expr '=>' expr ',' dict_entries : [{'$1','$3'}|'$5'].
  +dict_entries -> bool_expr '=>' expr : [{'$1','$3'}]. % FIXME: change add_expr to 1 below match
  +dict_entries -> bool_expr '=>' expr ',' dict_entries : [{'$1','$3'}|'$5'].
   
   Erlang code.
   
  
positive.code: Terminals
    eol '(' ')' '[' ']' '{' '}'
    float integer string atom regexp true false nil 
    identifier punctuated_identifier erl
    '+' '-' '*' '/' '%' '**' ',' '.' '..' '=' '=>' '$' ':'
    '===' '==' '!=' '>' '<' '>=' '<='
    '+=' '-=' '*=' '/=' '**='
  
negative.code:   max_expr
    function_identifier
    rebind_op
    bool_op
    comp_op
    add_op
    mult_op
  