Behaviour Preservation across Code Versions in Erlang

Listing 17

orddict_new.erl.

(1) -spec from_list(List) -> Orddict when

(2)   List:: [Key:: term(), Value:: term()],

(3)   Orddict:: orddict().

(4)

(5) from_list([]) -> [];

(6) from_list([_,_]=Pair) -> Pair;

(7) from_list(Pairs) ->

(8)   lists:ukeysort(1, reverse_pairs(Pairs, [])) % RIGHT

(9)   lists:ukeysort(1, Pairs).           % WRONG

(10)

(11) % ukeysort(N, TupleList1) -> TupleList2

(12) %   Returns a list containing the sorted elements of

(13) %   list TupleList1 where all except the first tuple of

(14) %   the tuples comparing equal have been deleted.

(15) %   Sorting is performed on the Nth element of the tuple

(16)

(17) reverse_pairs([_,_=H∣T], Acc) ->

(18)   reverse_pairs(T, [H∣Acc]);

(19) reverse_pairs([], Acc) -> Acc.