On Sat, Nov 27, 2010 at 10:45 AM, Eduardo Julian <eduardo...@gmail.com> wrote:
> user=> (let [a 'b] (str a))
> "b"
> user=> (let [b 5 a 'b] (eval a))
> java.lang.Exception: Unable to resolve symbol: b in this context
> (repl-1:7)
> user=> (let [a 'b b 5] (eval a))
> java.lang.Exception: Unable to resolve symbol: b in this context
> (repl-1:9)
>
> user=> (def b 5)
> #'user/b
> user=> (def a 'b)
> #'user/a
> user=> a
> b
> userr=> (eval a)
> 5
>
> How come this problem happens inside the let but not with def?
If you
(do
(binding [*ns* (find-ns 'foo)]
(eval bar)))
the evaluation of bar sees the global bindings in the namespace foo,
and can get at other global bindings and Java classes with
fully-qualified names, but cannot see the lexical environment around
the eval call. Even when called inside a let or a function body,
eval's contents only see what they would see if executed at the top
level of the source file for the namespace that is *current when eval
is called* (not necessarily the same file the eval itself is in).
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