On 2010 Apr 8, at 11:16 PM, Per Vognsen wrote:
It's not a defn thing. If you write (do (a) (b) (c)) at the REPL, you
should see the same exception.
Yes, I would expect that since at the REPL I am asking to have the
expression evaluated immediately.
Same with let.
Yet, if I say: '(do (a) (b) (c))
I do not get such an error, because quote is protecting me.
defn/fn are quoting in the sense that their body's expression is not
immediately evaluated,
yet they are doing more than quote because they're resolving the
symbols.
When the compiler sees a symbol in expression context, it first checks
whether it is bound in the local environment:
(let [x 42] x)
In this case, x is bound in the local environment.
If a symbol isn't bound in this way, the compiler will call (resolve
...) on the symbol at compile time. This yields some var v. The code
will then be evaluated as (deref v) at run time.
So how do I invoke that resolution machinery myself?
(my-do-later (a) (b 23) (c d e))
while the forms in the body of my-do-later will be spliced into other
places for later evaluation, I want to know that they're valid symbols
when my-do-later is called (which has to be a macro to delay
evaluation). I don't necessarily need or care to know what they are
resolved to (even regular code in clojure can be affected by binding
forms, which is what I'm planning to inject the bodies of my-do-later
forms into eventually).
Thanks,
-Doug
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