I want to convert [z,z,a,z,z,a,a,z]
to [{z,2},{a,1},{z,2},{a,2},{z,1}]
. How can I do it?
So, I need to accumulate previous value, counter of it and list of tuples.
I've create record
-record(acc, {previous, counter, tuples}).
Redefined
listToTuples([]) -> [];
listToTuples([H | Tail]) ->
Acc = #acc{previous=H, counter=1},
listToTuples([Tail], Acc).
But then I have some trouble
listToTuples([H | Tail], Acc) ->
case H == Acc#acc.previous of
true ->
false ->
end.
if you build up your answer (Acc) in reverse, the previous will be the head of that list.
here's how i would do it --
list_pairs(List) -> list_pairs(List, []).
list_pairs([], Acc) -> lists:reverse(Acc);
list_pairs([H|T], [{H, Count}|Acc]) -> list_pairs(T, [{H, Count+1}|Acc]);
list_pairs([H|T], Acc) -> list_pairs(T, [{H, 1}|Acc]).
(i expect someone will now follow with a one-line list comprehension version..)