MACD on Swipl

:-dynamic curr_ema/1.
:-dynamic curr_ema12_list/1.
:-dynamic curr_ema26_list/1.
:-dynamic curr_period_ptr/1.
:-dynamic ema_multiplier/1.
:-dynamic macd/1.

main:-
    create_candle_list,
    list_12_ema,
    list_26_ema,
    calculate_macd.



calculate_macd:-
    retract(curr_ema12_list(X)),
    retract(curr_ema26_list(Y)),
    Z is X-Y,
    asserta(macd(Z)),
    write(Z), nl,
    fail.

% This rule creates the candlestick list from the text file.

create_candle_list:-
    open("candlestick-data.txt", read, Str),
    read_file(Str, _),
    close(Str).

read_file(Stream, []) :-
    at_end_of_stream(Stream), !.

read_file(Stream,[X|L]) :-
    \+ at_end_of_stream(Stream),
    read(Stream, X),
    assert(X),
    write(X), nl,
    read_file(Stream, L).

% This is for calculating the 12-period EMA.

list_12_ema:-
    write('12-period EMA'),
    nl,
    fail.
list_12_ema:-                                           % reset current sma and period pointer values and ema multiplier
    retract(curr_ema(_)),
    asserta(curr_ema(0)),
    retract(ema_multiplier(_)),
    fail.
list_12_ema:-                                           % remove every ema listed so far
    retract(curr_ema12_list(_)),
    asserta(curr_ema12_list(0)),
    fail.
list_12_ema:-
    M is 2 / 13,
    asserta(ema_multiplier(M)),
    fail.
list_12_ema:-                                           % calculate the ema values
    candle(W, X, Close, Z),
    calculate_ema12_member(Close),
    fail.
list_12_ema:-                                           % display the ema values
    curr_ema12_list(X),
    write(X), nl,
    fail.

calculate_ema12_member(Close):-     % initialize things
    curr_ema12_list(Prev_Close),
    ema_multiplier(M),
    Prev_M is 1 - M,
    Prev_Weight is Prev_Close * Prev_M,
    Curr_Weight is Close * M,
    Curr_EMA is Prev_Weight + Curr_Weight,
    asserta(curr_ema12_list(Curr_EMA)),
    !.

% This is for calculating 26-period EMA.

list_26_ema:-
    write('26-period EMA'),
    nl,
    fail.
list_26_ema:-                                           % reset current sma and period pointer values and ema multiplier
    retract(curr_ema(_)),
    asserta(curr_ema(0)),
    retract(ema_multiplier(_)),
    fail.
list_26_ema:-                                           % remove every ema listed so far
    retract(curr_ema26_list(_)),
    asserta(curr_ema26_list(0)),
    fail.
list_26_ema:-
    M is 2 / 27,
    asserta(ema_multiplier(M)),
    fail.
list_26_ema:-                                           % calculate the ema values
    candle(W, X, Close, Z),
    calculate_ema26_member(Close),
    fail.
list_26_ema:-                                           % display the ema values
    curr_ema26_list(X),
    write(X), nl,
    fail.

calculate_ema26_member(Close):-     % initialize things
    curr_ema26_list(Prev_Close),
    ema_multiplier(M),
    Prev_M is 1 - M,
    Prev_Weight is Prev_Close * Prev_M,
    Curr_Weight is Close * M,
    Curr_EMA is Prev_Weight + Curr_Weight,
    asserta(curr_ema26_list(Curr_EMA)),
    !.

% This rule lists all the candles.

list_candles:-
    candle(W, X, Y, Z),
    write('candle('),
    write(W), write(', '),
    write(X), write(', '),
    write(Y), write(', '),
    write(Z), write(')'),
    nl, fail.

curr_candle([]).
curr_candle_list([]).
curr_ema(0).
curr_ema12_list([]).
curr_ema26_list([]).
curr_period_ptr(0).
max_period(0).