Added a new multi-threading predicate, threads/0, which prints a nicely formatted table of current threads and their status. Similar to the predicate with the same name on SWI-Prolog except that it does not join terminated threads.

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1658 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

docs/yap.tex

@@ -10153,6 +10153,12 @@ wait for the mutex.  The collistion-count is not available on
 Windows as this would break portability to Windows-95/98/ME or
 significantly harm performance.  Generally collision count is
 close to zero on single-CPU hardware.
+
+@item threads
+@findex threads/0
+@snindex threads/0
+@cnindex threads/0
+Prints a table of current threads and their status.
 @end table
 
 

pl/threads.yap

@@ -479,7 +479,6 @@ thread_local(X) :-
 	'$do_error'(type_error(callable,X),thread_local(Mod:X)).
 
 
-
 thread_sleep(Time) :-
 	var(Time), !,
 	'$do_error'(instantiation_error,thread_sleep(Time)).
@@ -521,3 +520,14 @@ thread_signal(Thread, Goal) :-
 	'$thread_self'(Id),
 	recorded('$thread_signal',[Id|G],R),
 	erase(R).
+
+
+threads :-
+	write('--------------------------------------------------------------'), nl,
+	format("~t~a~38+~n", 'Thread  Status'),
+	write('--------------------------------------------------------------'), nl,
+	current_thread(Thread, Status),
+	format("~t~q~30+  ~q~n", [Thread, Status]), 
+	fail.
+threads :-
+	write('--------------------------------------------------------------'), nl.