I did but it requires two levels of macro and that made me nervous.
The problem is derived values. When defining a binding, near as I can
tell, the values in the binding cannot see other values in the
binding. In other words:
(def *A* 10)
(binding [*A* 3 B (+ foo 1)] B)
Returns 11, not 4.
So to use the macro I have to:
(def *A* bogus_value)
(def B bogus_value)
(defmacro in-environment [env & body]
`(binding [*A* :A ..]
(binding [B (+ *A* 1)...]
~...@body))
I think this would actually work. But it requires a bunch of
accounting (all the bogus global defs) and introduces some worrisome
ordering issues. For example, let's say I have a value C whose
definition is (def C (+ B 1)). I can't define it using the previous
macro. Because, again, bindings can't see each other. So now I'd have
to write a macro that dynamically created a whole set of nested
bindings. Which seems like a lot of work.
In other words:
(binding [*A* :A...]
(binding [B (+ *A* 1)...]
(binding [C (+ *B* 1)...]
etc.
And I can't use let (which does allow for internal visibility) because
then other functions I call will bind to the global value not the let
value.
Yaron
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