Merge pull request #2767 from Kaiepi/scheduler

Document Scheduler.cue edge cases with :at/:in/:every

doc/Type/Scheduler.pod6

@@ -51,9 +51,14 @@ C<$times> tells the scheduler how many times to run the code.
 C<&catch> is called with the L<Exception|/type/Exception> as its sole argument
 if C<&code> dies.
 
+If C<$at>, C<$in>, or C<$every> are C<Inf>, C<&code> will never be run. If any
+of them are C<-Inf>, C<&code> will be run immediately. If any of them are
+C<NaN>, an C<X::AdHoc> exception will be thrown with the message "Cannot set
+NaN as a number of seconds".
+
 One should call the C<cancel> method on the returned C<Cancellation> object
 to cancel the (possibly repeated) cueing of the code.
 
 =end pod
 
-# vim: expandtab softtabstop=4 shiftwidth=4 ft=perl6
+# vim: expandtab softtabstop=4 shiftwidth=4 ft=perl6