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copied!<p>I do not have a solution for your problem, but I can't resist suggesting some improvement on the first two functions:</p> <pre><code>(defn extend-regs [reg s o] (let [os (get reg s)] (if (nil? os) (assoc reg s [o]) (assoc reg s (conj os o))))) ;; => place the 'if inside the assoc: (defn extend-regs [reg s o] (let [os (get reg s)] (assoc reg s (if (nil? os) [o] (conj os o))))) ;; => this (if (nil? x) ...) is the pattern of function fnil, so ... (defn extend-regs [reg s o] (let [os (get reg s)] (assoc reg s ((fnil conj []) os o)))) ;; with update-in, this will be even clearer, and we can remove the let altogether: (defn extend-regs [reg s o] (update-in reg [s] (fnil conj []) o)) </code></pre> <p>As for the second:</p> <pre><code>(defn add-reg! [d s o] (send d (fn [a] (assoc a :regs (extend-regs (:regs a) s o))))) ;; => We can, again, use update-in instead of assoc: (defn add-reg! [d s o] (send d (fn [a] (update-in a [:regs] extend-regs s o)))) ;; or, if you can get rid of extend-regs: (defn add-reg! [d s o] (send d (fn [a] (update-in a [:regs s] (fnil conj []) o))) </code></pre> <p>Finally, as a matter of style, I would place add-reg in a separate function, and directly use the idiom of sending to the agent in the client code (or have a simplified add-reg! function):</p> <pre><code>(defn add-reg [v s o] (update-in v [:regs s] (fnil conj []) o)) (defn add-reg! [d s o] (send d add-reg)) </code></pre> <p>I know this doesn't answer your initial question, but it was fun to write this step by step refactoring</p>

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