Études for Erlang

Solution 10-1

Here is a suggested solution for Étude 10-1.

phone_records.hrl

-record(phone_call,
  {phone_number, start_date, start_time, end_date, end_time}).

phone_ets.erl

%% @author J D Eisenberg <[e-mail]>
%% @doc Read in a database of phone calls
%% @copyright 2013 J D Eisenberg
%% @version 0.1

-module(phone_ets).
-export([setup/1, summary/0, summary/1]).
-include("phone_records.hrl").

%% @doc Create an ets table of phone calls from the given file name.

-spec(setup(string()) -> atom()).

setup(FileName) ->

  %% If the table exists, delete it
  case ets:info(call_table) of
    undefined -> false;
    _ -> ets:delete(call_table)
   end,

  %% and create it anew
  ets:new(call_table, [named_table, bag,
    {keypos, #phone_call.phone_number}]),

  {ResultCode, InputFile} = file:open(FileName, [read]),
  case ResultCode of
    ok -> read_item(InputFile);
    _ -> io:format("Error opening file: ~p~n", [InputFile])
  end.

%% Read a line from the input file, and insert its contents into
%% the call_table. This function is called recursively until end of file

-spec(read_item(file:io_device()) -> atom()).

read_item(InputFile) ->
  RawData = io:get_line(InputFile, ""),
  if
    is_list(RawData) ->
      Data = string:strip(RawData, right, $\n),
      [Number, SDate, STime, EDate, ETime] =
        re:split(Data, ",", [{return, list}]),
      ets:insert(call_table, #phone_call{phone_number = Number,
        start_date = to_date(SDate), start_time = to_time(STime),
        end_date = to_date(EDate), end_time= to_time(ETime)}),
      read_item(InputFile);
    RawData == eof ...