Your code is simple and easy to understand but it would look to see if
atoms can be removed. Also the use go/while loop makes your code not stop
and hence atom like @running is required.
This is my attempt to solve the problem. I started with your code as the
base and refactored it.
Following are the things which differ from your code:
- I have three channels customer-channel, waiting-room-channel,
barber-channel.
- Instead of keeping a @running atom, I made other functions like
waiting-room and barber to stop processing when the channel they are
dependent on is closed.
- Each channel maintain and return the customers they processed. So in the
end the barber channel returns all the customers it processed.
- I had the use mult channels for the customer channel since you are also
printing the total number of customers.
(require '[clojure.core.async :as async])
(do
(defn customers []
(let [c (async/chan)]
(async/go-loop [i 1]
(async/<! (async/timeout (+ 10 (rand-int 21))))
(when (async/>! c (str "Customer" i))
(recur (inc i))))
c))
(defn waiting-room [customer-channel]
(let [waiting-channel (async/chan (async/dropping-buffer 3))]
(async/pipe customer-channel waiting-channel)
waiting-channel))
(defn barber [waiting-channel]
(async/go-loop [processed-customers []]
(if-let [customer (async/<! waiting-channel)]
(do
(async/<! (async/timeout 100))
(recur (conj processed-customers customer)))
processed-customers)))
(let [customers-channel (customers)
customers-mult-channel (async/mult customers-channel)
all-customers-channel (async/tap customers-mult-channel
(async/chan))
saloon-customers-channel (async/tap customers-mult-channel
(async/chan))
saloon (-> saloon-customers-channel
waiting-room
barber)
customer-counter (async/reduce (fn [i c] (inc i)) 0
all-customers-channel)]
(async/<!! (async/timeout 1000))
(async/close! customers-channel)
(println "Haircuts for " (count (async/<!! saloon)) " customers out of
" (async/<!! customer-counter) " customers")))
On Sun, Jan 4, 2015 at 9:27 PM, Russell <[email protected]> wrote:
> Looks like the barber's loop doesn't check the "running" atom, so it will
> never stop...
>
> If you wanted to get rid of the atom for counting haircuts you could use a
> go-loop with a haircut count as an argument. Something like:
>
> (go-loop [haircuts 0]
> (if @running
> (do (cut-hair!)
> (recur (inc haircuts)))
> haircuts))
>
> Other than that, I'd find it easier to understand what the program was
> doing if you extracted out some of the code into functions named in the
> language of the domain. Even if all the cut-hair! function contains is (<!!
> (async/timeout 20)) it makes it easier to understand what that timeout
> *means*. Similarly, you could probably come up with a name for the
> channel passed to the barber function that's a bit more descriptive than
> "c" :-).
>
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