I'm trying to make a simple hangman game in SWI Prolog.   

Since we made this program run can you help me enchance the program with the following:   

***1)*** By keeping up with the letters that have been guessed so far. If the user guesses a letter that has already been guessed, the program should say 'You guessed that!' and just continue the game.

***2)*** Lastly, add a counter that counts the number of incorrect guesses and quits the game when a certain number is reached. The program should tell the user that they lose, display what the phrase really was, and terminate. Duplicate guesses should not be counted as wrong.  

**I would like to thank everyone who helped me so far. This means a lot to me.**

I provide you with the code and comments.

```
% This top-level predicate runs the game.  It prints a 
% welcome message, picks a phrase, and calls getGuess.

% Ans = Answer
% AnsList = AnswerList

hangman:- 
    getPhrase(Ans), 
    !, 
    write('Welcome to hangman.'),
    nl,
    name(Ans,AnsList), 
    makeBlanks(AnsList, BlankList), 
    getGuess(AnsList,BlankList).

% Randomly returns a phrase from the list of possibilities.

getPhrase(Ans):-
    phrases(L), 
    length(L, X), 
    R is random(X), 
    N is R+1, 
    getNth(L, N, Ans).

% Possible phrases to guess.

phrases(['a_picture_is_worth_a_thousand_words','one_for_the_money','dead_or_alive','computer_science']).

% Asks the user for a letter guess.  Starts by writing the 
% current "display phrase" with blanks, then asks for a guess and
% calls process on the guess.

getGuess(AnsList, BlankList):- 
    name(BlankName, BlankList), 
    write(BlankName), 
    nl,  
    write('Enter your guess, followed by a period and return.'), 
    nl, 
    read(Guess),
    !, 
    name(Guess, [GuessName]), 
    processGuess(AnsList,BlankList,GuessName).

% Process guess takes a list of codes representing the answer, a list of codes representing the current
% "display phrase" with blanks in it, and the code of the letter that was just guessed.  If the guess
% was right, call substitute to put the letter in the display phrase and check for a win.  Otherwise, just
% get another guess from the user.

processGuess(AnsList,BlankList,GuessName):- 
    member(GuessName,AnsList), 
    !,
    write('Correct!'),
    nl, 
    substitute(AnsList, BlankList, GuessName, NewBlanks), 
    checkWin(AnsList,NewBlanks).

processGuess(AnsList, BlankList,_):-
    write('Nope!'),
    nl,
    getGuess(AnsList, BlankList).

% Check to see if the phrase is guessed.  If so, write 'You win' and if not, go back and get another guess.

checkWin(AnsList, BlankList):- 
    name(Ans, AnsList), 
    name(BlankName, BlankList), 
    BlankName = Ans, 
    !, 
    write('You win!').

checkWin(AnsList, BlankList):- 
    !,
    getGuess(AnsList, BlankList).

% getNth(L,N,E) should be true when E is the Nth element of the list L. N will always
% be at least 1.

getNth([H|T],1,H).

getNth([H|T],N,E):-
    N1 is N-1,
    getNth(T,N1,E1),
    E=E1.

% makeBlanks(AnsList, BlankList) should take an answer phrase, which is a list
% of character codes that represent the answer phrase, and return a list
% where all codes but the '_' turn into the code for '*'.  The underscores
% need to remain to show where the words start and end.  Please note that 
% both input and output lists for this predicate are lists of character codes.
% You can test your code with a query like this:
% testMakeBlanks:- name('csc_is_awesome', List), makeBlanks(List, BlankList), name(Towrite, BlankList), write(Towrite). 

makeBlanks(AnsCodes, BlankCodes) :-
  maplist(answer_blank, AnsCodes, BlankCodes).

answer_blank(Ans, Blank) :-
  Ans == 0'_ -> Blank = Ans ; Blank = 0'* .

% substitute(AnsList, BlankList, GuessName, NewBlanks) Takes character code lists AnsList and BlankList, 
% and GuessName, which is the character code for the guessed letter.  The NewBlanks should again be a 
% character code list, which puts all the guesses into the display word and keeps the *'s and _'s otherwise.
% For example, if the answer is 'csc_is_awesome' and the display is 'c*c_**_*******' and the guess is 's', the 
% new display should be 'csc_*s_***s***'.
% You can test your predicate with a query like this:
% testSubstitute:- name('csc_is_awesome', AnsList), name('c*c_**_*******', BlankList), name('s',[GuessName]), substitute(AnsList, BlankList, GuessName, NewBlanks),
%    name(Towrite, NewBlanks), write(Towrite). 

% Also, since the predicate doesn't deal directly with character codes, this should also work:
% substitute(['c','s','c'],['c','*','c'],'s',L).  L should be ['c','s','c'].

substitute(AnsCodes, BlankCodes, GuessName, NewBlanks) :-
     maplist(place_guess(GuessName), AnsCodes, BlankCodes, NewBlanks).

place_guess(Guess, Ans, Blank, Display) :-
    Guess == Ans -> Display = Ans ; Display = Blank.

```