Merge sorting with inversions counting

sort.erl

-module('sort').
-export([start/0]).

start() ->
  Ctr = spawn_link(counter, loop, [0]),
  {ok, Data} = getData(),
  {ok, _Sorted} = sortData(Data, Ctr),
  counter:get_count(Ctr) .

getData() ->
  {ok, Data} = readfile('IntegerArray.txt'),
  {ok, Data}.

readfile(FileName) ->
  {ok, Binary} = file:read_file(FileName),
  Strings = string:tokens(erlang:binary_to_list(Binary), "\r\n"),
  Integers = lists:map(fun(X) -> list_to_integer(X) end, Strings),
  {ok, Integers}.

sortData(List, Ctr) ->
  Sorted = mergesort(List, Ctr),
  {ok, Sorted}.

mergesort([], _) -> [];
mergesort([X], _) -> [X];
mergesort(List, Ctr) ->
   {Left, Right} = lists:split(length(List) div 2, List),
   merge(mergesort(Left, Ctr), mergesort(Right, Ctr), Ctr).

merge(List, [], _) -> List;
merge([], List, _) -> List;
merge([A | Tail1] = Left, [B | Tail2] = Right, Ctr) ->
  if
   A < B ->
      [A | merge(Tail1, Right, Ctr)];
   true ->
      % {ok, Count} = file:read_file('count'),
      % NewCount = binary_to_term(Count) + length(Left),
      % file:write_file('count', term_to_binary(NewCount)),
      Length = length(Left),
      Ctr ! {incr, Length},
      [B | merge(Left, Tail2, Ctr)]
  end.