This is a interesting side-effect of the way that map< is implemented. Internally map< is not actually using channels, but is using the channel protocols. It's creating something that looks like a ReadPort, but before handing values to callbacks it applies a function to the value. So map< doesn't actually create a channel at all.
I actually didn't think about this until today (Rich wrote the original code), it's a rather neat way to go about. Timothy On Mon, Apr 7, 2014 at 9:26 AM, Alejandro Ciniglio <[email protected]>wrote: > Using core.async, I've understood the convention to be that if you take > nil from a channel, that channel is closed. This seems to hold for most > cases, but I've found a corner case when using map< that lets you pull nil > from a channel that is not closed. > > (def a (chan)) > (def c (map< seq a)) > (go (prn (<! c))) > (>!! a []) > ; => nil nil ;; [one nil is printed, one is returned] > (go (prn (<! c))) > (>!! a [1]) > ; => nil (1) > > This can be chained as well (e.g. (map< identity (map< seq a)) ), and > nils just flow through. > > From looking at the implementation, it's apparent that this happens > because the function application of map happens when taking from the output > channel so nil is not technically on the channel, (unless it flows through > to another map). > > Is this a bug or is my mental model of nil => closed incorrect? > > Thanks, > Alejandro > > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to [email protected] > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- "One of the main causes of the fall of the Roman Empire was that-lacking zero-they had no way to indicate successful termination of their C programs." (Robert Firth) -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to [email protected] Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
