CSV parsing
Dear author, @ferd, I am solely out of positive motives and a desire to improve the books, I would like to suggest that you think about update the section without the help of the maps module functionality in future editions of your very informative and useful book. As shown by the working tests and the implementation that I did without using this module, but using an older ones (lists, proplists) (and as the last test convincingly showed) - the maps module is not the best and not very visual solution for this task, moreover, it has limitations in which there is no need.
%% @doc this counterexample is taken literally from the RFC and cannot
%% work with the current implementation because maps have no dupe keys
dupe_keys_unsupported_test() ->
CSV = "field_name,field_name,field_name\r\n"
"aaa,bbb,ccc\r\n"
"zzz,yyy,xxx\r\n",
[Map1, Map2] = bday_csv:decode(CSV),
%?debugFmt("Map1 = ~p~nMap2 = ~p~n", [Map1, Map2]),
%?debugFmt("Map2 = ~p~n",[Map2]),
?assertEqual(1, length(maps:keys(Map1))),
?assertEqual(1, length(maps:keys(Map2))),
?assertMatch(#{"field_name" := _}, Map1),
?assertMatch(#{"field_name" := _}, Map2).
See what we can get by simplifying our CSV parser implementation:
%% @doc this counterexample is taken literally from the RFC
dupe_keys_unsupported_test() ->
CSV = "field_name,field_name,field_name\r\n"
"aaa,bbb,ccc\r\n"
"zzz,yyy,xxx\r\n",
Result = bday_csv_tuple:decode(CSV),
List = lists:flatten(Result),
?assertEqual(6, length(List)),
lists:foreach(fun(Elem) -> ?assertMatch({"field_name", _}, Elem) end, List).
Link to source code