anchor.diff:  
   try_represent_token(Repr, Node,
     #yaml_scalar{tag = #yaml_tag{uri = {non_specific, "?"}},
  -  text = Text} = Token) when
  -  Text == "true" orelse
  -  Text == "True" orelse
  -  Text == "TRUE" orelse
  -  Text == "false" orelse
  -  Text == "False" orelse
  -  Text == "FALSE" ->
  +  text = Text} = Token) when ?IS_TRUE(Text) orelse ?IS_FALSE(Text) ->
       represent_token(Repr, Node, Token);
   try_represent_token(_, _, _) ->
       unrecognized.
   
   represent_token(#yaml_repr{simple_structs = true},
  -  undefined, #yaml_scalar{text = Text}) when
  -  Text == "true" orelse
  -  Text == "True" orelse
  -  Text == "TRUE" ->
  +  undefined, #yaml_scalar{text = Text}) when ?IS_TRUE(Text) ->
       {finished, true};
   represent_token(#yaml_repr{simple_structs = true},
  -  undefined, #yaml_scalar{text = Text}) when
  -  Text == "false" orelse
  -  Text == "False" orelse
  -  Text == "FALSE" ->
  +  undefined, #yaml_scalar{text = Text}) when ?IS_FALSE(Text) ->
       {finished, false};
   represent_token(#yaml_repr{simple_structs = false},
  -  undefined, #yaml_scalar{text = Text} = Token) when
  -  Text == "true" orelse
  -  Text == "True" orelse
  -  Text == "TRUE" ->
  +  undefined, #yaml_scalar{text = Text} = Token) when ?IS_TRUE(Text) ->
       Pres = yaml_repr:get_pres_details(Token),
       Node = #yaml_bool{
         module = ?MODULE,
  
positive.code:     },
      {finished, Node};
  represent_token(#yaml_repr{simple_structs = false},
    undefined, #yaml_scalar{text = Text} = Token) when
    Text == "false" orelse
    Text == "False" orelse
    Text == "FALSE" ->
      Pres = yaml_repr:get_pres_details(Token),
      Node = #yaml_bool{
        module = ?MODULE,
  
negative.code: 
  -define(TAG, "tag:yaml.org,2002:bool").
  
  -define(IS_TRUE(S),
    S == "true" orelse S == "True" orelse S == "TRUE" orelse
    S == "y" orelse S == "Y" orelse
    S == "yes" orelse S == "Yes" orelse S == "YES" orelse
    S == "on" orelse S == "On" orelse S == "ON").
  
  -define(IS_FALSE(S),
    S == "false" orelse S == "False" orelse S == "FALSE" orelse
    S == "n" orelse S == "N" orelse
    S == "no" orelse S == "No" orelse S == "NO" orelse
    S == "off" orelse S == "Off" orelse S == "OFF").
  
  %% -------------------------------------------------------------------
  %% Public API.
  %% -------------------------------------------------------------------
  