make commands for adding new requirements

todo.pl

@@ -28,10 +28,35 @@ list_done :- all_tasks(L, done), print_task_list(L,1).
 print_list([]).
 print_list([H|T]) :- write(H),nl, print_list(T).
 
+new(X) :- 
+    task(X, todo), 
+    write("task already exist"),
+    !.
 new(X) :- 
     asserta(task(X, todo)), 
     write("added task "), 
     write(X).
+new(X,Y) :- idx(Y, Task), new(X, Task).
+new(X,Y) :- 
+    asserta(task(X, todo)), 
+    asserta(requires(X, Y)), 
+    write("added task "), 
+    write(X),
+    write(" as a subtask for "), 
+    write(X).
+depend(X,Y) :- idx(X, Task), depend(Task, Y).
+depend(X,Y) :- idx(Y, Task), depend(X, Task).
+depend(X,Y) :- 
+    task(X, todo),
+    task(Y, _),
+    asserta(requires(X, Y)).
+depend(X,Y) :- 
+    task(X, done),
+    task(Y, _),
+    retractall(task(Y, _)),
+    asserta(task(Y, todo)),
+    asserta(requires(X, Y)).
+
 check(X) :- idx(X, Task), check(Task).
 check(X) :- 
     task(X, todo),