Franck’s index.erl

-module(index). 
-export([index_file/1]).

readlines(Name) -> 
    {ok,File} = file:open(Name,[read]), 
    extract_content(File,[]).

extract_content(File,Partial) -> 
    case io:get_line(File,"") of 
        eof -> file:close(File), Partial; 
        Line -> {Strip,_} = lists:split(length(Line)-1,Line), extract_content(File,Partial ++ [Strip]) 
    end.

show_file_contents([L|Ls]) -> 
    io:format("~s~n",[L]), 
    show_file_contents(Ls);

show_file_contents([]) -> ok.

nopunct([]) -> []; 
nopunct([X|Xs]) -> 
    case lists:member(X,".,;:\t\n\'\"") of 
        true -> nopunct(Xs); 
        false -> [X|nopunct(Xs)] 
    end.

dedup([],Y) -> Y; 
dedup([X|Xs],Y) -> 
    case lists:member(X,Y) of 
        false -> dedup(Xs,[X|Y]); 
        true -> dedup(Xs,Y) 
    end.

make_index([],Y,_) -> Y; 
make_index([X],Y,_) -> Y ++ [{X,X}]; 
make_index([X,Nx|Xs],Y,Z) -> 
    case Nx == (X + 1) of 
        true -> make_index([Nx|Xs], Y, Z); 
        _ -> make_index([Nx|Xs], Y ++ [{Z,X}], Nx) 
    end.

combine_indices({X,I}, []) -> [{X,I}]; 
combine_indices({X,I}, [{Y,Indices}|Ys]) -> 
    case X == Y of 
        true -> [{Y, Indices ++ I} | Ys]; 
        _ -> [{Y,Indices}|combine_indices({X,I},Ys)] 
    end.

index_words([], Word) -> Word; 
index_words(Word, []) -> Word; 
index_words([X|Xs], Y) -> index_words(Xs,combine_indices(X,Y)).

create_word_index([], Y, _) -> Y; 
create_word_index([L|Ls], Y, N) -> 
    Words = string:tokens(nopunct(L)," "), 
    Entries = dedup(Words, []), 
    Indexes = lists:map(fun(X) -> {X,[N]} end, Entries), 
    create_word_index(Ls, index_words(Indexes,Y), N+1).

index([]) -> []; 
index(Lines) -> 
        lists:map(fun({Word, AllLines}) -> 
            {Word, make_index(AllLines, [], hd(AllLines))} 
        end, Lines).

% USAGE 
% index:index_file("./gettysburg-address.txt").

index_file(Name) -> 
    Lines = readlines(Name), 
    Indices = create_word_index(Lines,[],1), 
    index(Indices).