Another possibility is to send a message on a channel when the user is set, and then just wait with `sync` for a message to appear on the channel.
Sam On Fri, Mar 19, 2021 at 12:02 PM Jay McCarthy <[email protected]> wrote: > > The best thing is to use a semaphore instead of a mutable reference. > If you can't do that, then I think that you should combine the mutable > reference with a signaling semaphore. If you can't do that, then I > can't think of anything but a poll. > > -- > Jay McCarthy > Associate Professor @ CS @ UMass Lowell > http://jeapostrophe.github.io > Vincit qui se vincit. > > On Fri, Mar 19, 2021 at 11:59 AM David Storrs <[email protected]> wrote: > > > > Suppose I have a function that tests for some condition, e.g. > > > > (define current-user (make-parameter #f)) > > (define (current-user-set?) (not (false? (current-user))) > > > > What is the best way to say "wait until 'current-user-set?' returns true"? > > I've been through the Events chapter in the Reference and nothing seems > > like a great fit. I could do polling via sleep or alarm-evt but that seems > > inefficient. Is there a better way? > > > > -- > > You received this message because you are subscribed to the Google Groups > > "Racket Users" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to [email protected]. > > To view this discussion on the web visit > > https://groups.google.com/d/msgid/racket-users/CAE8gKocbPgjcFAF_o2g6mhZBEH8PpeGyJ4CwznKc3DZkMjY%3DGw%40mail.gmail.com. > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/racket-users/CAJYbDanE4zqgFRAFSYs4kdLzjKf9xg3xi0JMNU7VmFREstNBgQ%40mail.gmail.com. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAK%3DHD%2BZbgPu734nDR408MGnvLG_tbfzeHp8TeiJ0546Fu8zVKQ%40mail.gmail.com.
