I apologize, apparently you can't use go-loop how I did below,
=> (def my-go-loop (async/go-loop [msg (async/<! c)] (println "got msg "
msg " from channel " 'c)))
...try this instead:
(def my-go-loop (async/go-loop [] (let [msg (async/<! c)] (println "got
msg " msg " from channel " 'c))))
Sorry about that!
DD
(2014/05/12 13:21), Dave Della Costa wrote:
>
>> 1) I feel like it is a redundant to define bindings multiple times in
>> my go's let exprs when the params have already been passed in as
>> arguments. Is there a more idiomatic way to do this?
>
> I think the fact that you are re-binding in a let should show you that
> these variables are already in scope: that let is wholly redundant, just
> remove it.
>
>
>> 2) Whenever I try to create a generic process to automatically
>> generate a log-name for each channel and then call update, I get a
>> 'symbol cannot be cast to atom' error. How can I get around this? It
>> seems to happen even if I don't use the log-name function.
>
> It's simple: a symbol is not an atom. It's telling you exactly what you
> need to know: you cannot call swap! on a symbol. Make sure your atom is
> the first argument to swap! wherever you use it.
>
>
>> 3) Is there a better way to keep track of what's on a channel that
>> doesn't use macros?
>
> You cannot look inside of a channel, but to do what you want and get a
> sense of how core.async works, I think you are on the right track by
> logging as you put stuff in and take it out.
>
> That said, I would start by getting rid of the log and the macro--these
> are unnecessary complications--and do things very simply:
>
> => (require '[clojure.core.async :as async])
> nil
> => (def c (async/chan))
> #'user/c
> => (def my-go-loop (async/go-loop [msg (async/<! c)] (println "got msg "
> msg " from channel " 'c)))
> #'user/my-go-loop
> => (defn put-and-print! [c msg] (println "putting msg " msg " onto
> channel " 'c) (async/put! c msg))
> #'user/put-and-print!
> => (put-and-print! c "I am a message!")
> putting msg I am a message! onto channel c
> got msg I am a message! from channel c
> nil
> =>
>
> Printing out "channel c" is kind of silly since there is only one, but
> it sounds like you may want to do this with multiple channels so this is
> one way to print out the variable name--simply quote it.
>
> DD
>
> (2014/05/12 11:41), gamma235 wrote:
>> Hi everyone,
>>
>> I am getting my feet wet with core.async and am trying to attach atoms
>> to channels that update automatically and print out to the console as
>> you take and put. This is not for anything serious, just a way to get
>> familiar with the behavior and functionality of the library and practice
>> my Clojure skills. Thanks in advaan
>>
>> Here is my code:
>>
>> (defn log-name [ch] (symbol (str ch '-log)))
>>
>> ;; Is this efficiently written?
>> (defmacro transparent-chan [ch]
>> (do
>> `(def ~ch (chan))
>> `(def (log-name ~ch) (atom []))
>> `(println "new transparent channel created!")))
>>
>> (defn- update [log v]
>> (do
>> (swap! log conj v)
>> (println "log test passed: " v " has been logged")
>> (println "channel contents: " @log)))
>>
>> (defn transparent-put [ch v]
>> (let [log (log-name ch)]
>> (go
>> (let [ch ch
>> v v]
>> (>! ch v)
>> (println v " has been successfully moved through the channel")))
>> (update log v)
>> (println "put test passed: " v " has been put on the channel")
>> (println " rechecking channel contents: " @log)))
>>
>> (defn transparent-take [ch]
>> (go
>> (let [v (<! ch)
>> log-name (symbol (str ch '-log))]
>> (swap! log-name #(remove #{v} %))
>> (println v "has been removed from channel")))
>> (println " removal pending"))
>>
>>
>>
>> ;; tests
>> (transparent-chan c)
>> c
>> c-log
>> @c-log
>> (transparent-put c 42)
>> (transparent-take c)
>>
>>
>>
>> My main questions are regarding variable scope:
>> 1) I feel like it is a redundant to define bindings multiple times in my
>> go's let exprs when the params have already been passed in as arguments.
>> Is there a more idiomatic way to do this?
>>
>> 2) Whenever I try to create a generic process to automatically generate
>> a log-name for each channel and then call update, I get a 'symbol cannot
>> be cast to atom' error. How can I get around this? It seems to happen
>> even if I don't use the log-name function.
>>
>> 3) Is there a better way to keep track of what's on a channel that
>> doesn't use macros?
>>
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