first commit

data.pl

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+task("take over a world",todo).
+task("sleep",done).
+task("finish this",todo).
+task("test task",todo).

todo.pl

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+:- dynamic task/2.
+:- dynamic requires/2.
+:- discontiguous load/0.
+    
+task("take over a world", todo).
+task("sleep", done).
+task("finish this", todo).
+
+all_tasks(L):- findall(X, task(X, _), L).
+all_tasks(L, STATE):- findall(X, task(X, STATE), L).
+
+print_task_list([]).
+print_task_list([H|T]) :- task(H,ISDONE), write(ISDONE),write(': '), write(H),nl, print_task_list(T).
+
+list :- all_tasks(L), print_task_list(L).
+
+print_list([]).
+print_list([H|T]) :- write(H),nl, print_list(T).
+
+new(X) :- asserta(task(X, todo)), write("added task "), 
+write(X).
+check(X) :- task(X, todo), asserta(task(X, done)), retractall(task(X, todo)), 
+write("marked task "), write(X), write(" as done").
+
+
+save_task(Task, Stream) :-
+    task(Task, State),
+    write_canonical(Stream, task(Task, State)),
+    write(Stream, '.').
+
+save_task_list([Task], Stream) :- 
+    save_task(Task, Stream).
+
+save_task_list([H|T], Stream) :- 
+    save_task(H, Stream),
+    write(Stream, '\n'),
+    save_task_list(T, Stream).
+
+save :-
+    all_tasks(L), 
+    open('data.pl', write, Stream), 
+    save_task_list(L, Stream),
+    close(Stream).
+
+
+load_task(Stream) :- 
+    read(Stream, Task),
+    Task = end_of_file,
+    close(Stream).
+
+load_task(Stream) :- 
+    read(Stream, Task),
+    asserta(Task),
+    load_task(Stream).
+load :-
+    open('data.pl', read, Stream),
+    load_task(Stream).
+
+clear :- retractall(task(_, _)).
+
+consult(data).