Hi all,
I'm building an application in which I want some function calls to be
logged. However, when I have function A and B (both will be logged)
and A is called from B, I want the log to show this relation. I
defined a small macro for this purpose:
(def *hierarchy* [])
(def *action-id* nil)
(defn action-id []
(if (nil? *action-id*)
(gensym "action-")
*action-id*))
(defmacro defalgo [name args & body]
`(defn ~name ~args
(do (binding [*hierarchy* (conj *hierarchy* (str ~name))
*action-id* (action-id)]
(log *action-id* *hierarchy*)
~...@body))))
Any top level calls of functions defined with defalgo will be logged
with a different id because of the gensym. Functions called from
within the toplevel call will be logged with the same id as the
toplevel call. This all works perfectly fine. Why post this then?
I was testing this mechanism with a loop to simulate the recursive
bindings and I got some unexpected behavior.
(defn action-id []
(if (nil? *action-id*)
(gensym "action-")
*action-id*))
(defn action-id-test []
(loop [counter 0]
(binding [*action-id* (action-id)]
(println *action-id*)
(if (< counter 3)
(recur (inc counter))
nil))))
Executing from the repl gave this result:
nl.tbb.cometucoco=> *action-id*
nil
nl.tbb.cometucoco=> (action-id-test)
action-5177
action-5177
action-5177
action-5177
nil
nl.tbb.cometucoco=> *action-id*
action-5177
nl.tbb.cometucoco=> (set! *action-id* nil)
nil
nl.tbb.cometucoco=> (action-id-test)
action-5184
action-5184
action-5184
action-5184
nil
nl.tbb.cometucoco=> *action-id*
action-5184
*action-id* isn't rebound to its initial value. This only happens when
the binding occurs inside the loop. This isn't the expected behavior
right? Why is *action-id* sticky??
Vincent
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