wordsort_sequential.erl

-module(wordsort_sequential).
-export([start/1, start_file/1]).
-import(dict, [store/3, find/2]).
-author({"Christopher Bertels", "[email protected]"}).

start(String) ->
    process(words(String)).


start_file(Filename) ->
    {ok, File} = file:open(Filename, [read]),
    process(words_from_lines(read_lines(File))).
    


process(Words) ->
    WordDict = count_words(Words, dict:new()),
    SortedWords = sorted_words(WordDict),
    io:format("counted ~p words in total. Sorted word list following...~n", [length(Words)]),
    WordDict,
    lists:foreach(fun (Word) ->
			  {ok, WordCount} = find(Word, WordDict),
			  io:format("~p : ~p~n", [WordCount, Word])
		  end,
		  SortedWords).



read_lines(Fd) ->
    read_lines(Fd, []).

read_lines(Fd, LineBuffer) ->
    case io:get_line(Fd, "") of
	eof ->
	    LineBuffer;
	Line ->
	    case Line -- "\n" of
		"" ->
		    read_lines(Fd, LineBuffer);
		GoodLine ->
		    read_lines(Fd, [GoodLine | LineBuffer])
	    end
    end.


%% returns all words of a string as a list.
words(String) ->
    string:tokens(String, " ").


words_from_lines(Lines) ->
    lists:foldl(fun lists:append/2, 
		[],
		lists:map(fun(Line) ->
				  words(Line)
			  end,
			  Lines)).

%% increments the word's counter by 1 in Dict
count_word(Word, Dict) ->
    case find(Word, Dict) of
	{ok, Val} ->
	    store(Word, Val + 1, Dict);
	_ ->
	    store(Word, 1, Dict)
    end.


%% count all words in list and store results in Dict.
count_words([], Dict) ->
    Dict;
count_words([Word|Rest], Dict) ->
    count_words(Rest, count_word(Word, Dict)).


%% sort dictionary by values
sorted_words(Dict) ->
    lists:sort(fun(X, Y) -> dict:find(X, Dict) >= dict:find(Y, Dict) end, 
	       dict:fetch_keys(Dict)).