Not at all answering your question, but I would strongly suggest to at least
deref `me` before calling the function, so it’s definition would be more like:
(defn svr [me slot]
(when-let [sval (slot me)]
(if (jz-ref sval)
(condp type @sval)
:jzi (:val @sval)
:jzf ((:rule @sval) me)
(error “jz-ref? type unknown”))
sval)))
And I’d probably extract the body of if into a separate function
(defn- body-of-if [me sval]
(if (jz-ref sval)
(condp type sval)
:jzi (:val sval)
:jzf ((:rule sval) me)
(error “jz-ref? type unknown”))
sval))
so that your svr would end up something like
(defn svr [slot me]
(when-let [sval (slot me)]
(body-of-if me @sval))
and then you’d call svr as
(svr @me slot)
This way, your functions don’t need to know that their arguments happen to be
atoms/refs, and they fit nicely in with eg
(swap! atom-that-contains-me svr slot)
But I do agree with Timothy that you should probably try to keep your data
structure free of atoms, and just use one atom to hold your data structure.
Erik.
> On 1. apr. 2016, at 07.37, hiskennyness <[email protected]> wrote:
>
> With Jellz (ne Cells in CL) I want to make reading an attribute of an object
> seem like a normal function call, but reading a cell actually looks like this:
>
> (defn- svr [slot me] ;; svr = slot-value-read, me = short version of "self"
> (when-let [sval (slot @me)]
> (cond
> (jz-ref? sval)
> (case (type @sval)
> :jzi (:val @sval)
> :jzf ((:rule @sval) me)
> (error "jz-ref? type unknown" ))
> :else sval)))
>
> svr is internal because I plan to hide it. Instead of coding (svr :mass
> kenny) I want to code (mass kenny). And instead of hand-coding:
>
> (defn mass [me] (svr :mass me))
>
> ...I want to code (jz/def-jzo-slot :mass).
>
> (defmacro def-jzo-slot [slot]
> `(defn ~(symbol (subs (str slot) 1)) [~'me]
> (com.tiltontec.jellz.api/svr ~slot ~'me)))
>
> That worked fine until I moved my testing hacks into a proper test file in
> the test hierarchy and Clojure complained that svr was internal (I forget the
> exact language).
>
> I broke down and made it defn instead of defn-, but was something else going
> on? I am used to Common Lisp which sees what I am up to and worries about the
> symbol being defined in the Cells package, not the package into which the
> macroexpansion will be happening.
>
> I always thought that was very clever and classically XWIW (exactly what I
> want), btw.
>
> This is not a big deal, but did I miss some way of keeping svr internal?
>
> -kt
>
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