Behaviour Preservation across Code Versions in Erlang

Listing 2

happy1.erl.

(1) is_happy(X, XS) ->

(2)  if

(3)   X == 1 -> true;

(4)   X < 1 -> false;

(5)   true ->

(6)    case member(X, XS) of

(7)     true -> false;

(8)     false ->

(9)      is_happy(sum(map(fun(Z) -> ZZ end,

(10)       [Y - 48 ∣∣ Y <- integer_to_list(X)])),

(11)        [X∣XS])

(12)    end

(13)  end.

(14) happy(X, Top, XS) ->

(15)  if

(16)   length(XS) == Top -> sort(XS);

(17)   true ->

(18)    case  is_happy(X,[]) of

(19)     true -> happy(X + 1, Top, [X∣XS]);

(20)     false -> happy(X + 1,Top, XS)

(21)    end

(22)  end.

(23)

(24) -spec main(pos_integer(),pos_integer()) ->

(25)  [pos_integer()].

(26) main(N, M) ->

(27)  happy(N, M, []).

(28)