Hi,
On Aug 10, 9:10 pm, jvt <vincent.to...@gmail.com> wrote:
> Be this as it may, you can still get weird run-time behavior from this
> kind of macro in the following situation:
>
> (def *v1* 10)
> (def var-map {:*v1* 100})
> (def wrong-map {:*v2* 10})
>
> (with-bindings-from-map var-map (+ v1 100)) ; -> 200, does what we
> expect
> (with-bindings-from-map wrong-map (+ v1 100)) ; -> 110, does the
> wrong thing entirely, silently
The map actually takes the Var itself as key. (def wrong-map {#'*v2*
10})
already blows up, if *v2* does not exist. If it does exist, we are in
the
same situation you have when the key is not present in the map.
But in this situation we are all the time: (:some-key a-map). You type
by accident (:sone-key a-map) and maybe don't notice it until strange
things happen, because the value of ":some-key" is suddenly nil.
If you are concerned about this, you can always add your function
on top of the proposed low-level API to add all safety-checks needed.
While at the moment this is not possible at all...
> Plus, this doesn't depend on a how the compiler implements or
> optimizes names. It could be that in the future clojure will want to
> use a different representation internally than maps for symbol->value
> translation.
No. It is already independent of the Compiler. The map is
just used to transport the mapping to the Compiler. What
he does internally with the map is completely independent
of that fact. He may use the map directly or do some further
magic to it.
The only hacky point is that Var/pushThreadBindings is not
a public API up-to-now. But Rich already stated his wish to
slate this into a Clojure API via push-thread-bindings.
Sincerely
Meikel
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