/* Same as tableread3, but perturbation of threads occurs at a
different place.  Am unsure of the semantics of backtracking over
join_list -- but we do need to handle it somehow */


:- dynamic num_is/1.

:- assert((concurr_initialize(tableread(N,_)):- 
		retractall(num_is(_)),
		assert(num_is(N)),
		(tableread_table(_),fail;true))).

:- table tableread_table/1.

% This isn't good tabling style, but does make a good test.
tableread_table(X):- 
	test_thread_number(Threads),
	num_is(N),
	Spin is 10 * N,
	make_duplicate_goals(Threads,spin(Spin),List),
	exec_goals(List,Ids),
	for(X,1,N),
	join_list(Ids).

spin(N):- 
	num_is(N),
	for(_X,1,N),
	fail.
spin(_).

tableread(_,Str):- 
	tableread_table(X),
	writeln(Str,X),
	fail.
tableread(_,_).
	
%%% for(?I,+B1,+B2) nondeterministically binds I to all integer values
%%% from B1 to B2.  B1 and B2 must be integers, but either may be larger.
for(I,B1,B2) :-
	(B1 =< B2
	 ->	forup(I,B1,B2)
	 ;	fordown(I,B1,B2)
	).

forup(L,L,H) :- L =< H.
forup(I,L,H) :- L < H, L1 is L+1, forup(I,L1,H).

fordown(H,H,L) :- H >= L.
fordown(I,H,L) :- H > L, H1 is H-1, fordown(I,H1,L).