anchor.diff:  -module('clock').
   
   -export([create/2,
  -         is_equal/2,
  -         minutes_add/2,
  -         minutes_delete/2,
  -         to_string/1] ).
  +  is_equal/2,
  +  minutes_add/2,
  +  to_string/1]).
   
   -record(?MODULE, {normalized}).
   
  
positive.code: -define(MINUTES_PER_DAY, (?HOURS_PER_DAY * ?MINUTES_PER_HOUR)).
  
  
  create(Hour,Minutes) ->
    #?MODULE{normalized = mod(Hour * ?MINUTES_PER_HOUR + Minutes, ?MINUTES_PER_DAY)}.
  
  is_equal(C, C) ->
  
negative.code: is_equal(_, _) ->
    false.
  
  minutes_add(#?MODULE{normalized = Mins}, Minutes) ->
    TotalMinutes = mod(Mins + Minutes, ?MINUTES_PER_DAY),
    #?MODULE{normalized = TotalMinutes}.
  
  to_string(#?MODULE{normalized = Mins}) ->
    Hour = Mins div ?MINUTES_PER_HOUR,
    Minutes = Mins rem ?MINUTES_PER_HOUR,
    lists:flatten(io_lib:format("~2.10.0b:~2.10.0b", [Hour, Minutes])).
  
  mod(X, Y) when X > 0 -> X rem Y;
  mod(X, Y) when X < 0 -> Y + X rem Y;
  mod(0, _Y) -> 0.
  