使用~w来格式化整数，而不是~s。

-module(main).
-export([sort_of_sum/1]).

sort_of_sum([]) ->
    io:format("There is nothing there!~n");
sort_of_sum([H]) ->
    io:format("The sum is ~w.~n", [H]);
sort_of_sum([H1, H2]) ->
    io:format("The sum is ~w.~n", [H1 + H2]);
sort_of_sum([H1, H2, H3]) ->
    io:format("The sum is ~w.~n", [H1 + H2 + H3]);
sort_of_sum([_H | _T]) ->
    io:format("That's too many to add!~n");
sort_of_sum(_) ->
    io:format("I can't add that!~n").