Thanks! That got me back on track. I'm off and running on my DSL:
(defmacro sketch
[title & code]
(let [code-map (assemble-map #{:setup :draw} :draw code)
setup-slice (:setup code-map)
draw-slice (:draw code-map)]
`(let [setup-fn# (to-fn ~setup-slice)
draw-fn# (to-fn ~draw-slice)]
(run-sketch ~title setup-fn# draw-fn#))))
It's a bit challenging at first; I was very concerned with symbol name
collisions ... it takes a bit to realize that symbols you use in a
macro body (that are not part of the back quoted template) can't
conflict with symbols in forms passed to the macro; by the time those
passed forms are ever evaluated, the (let) in the macro is long gone
and the namespaces are clean.
On Tue, Mar 10, 2009 at 12:30 PM, Chouser <chou...@gmail.com> wrote:
>
> On Tue, Mar 10, 2009 at 2:45 PM, Howard Lewis Ship <hls...@gmail.com> wrote:
>>
>> (defmacro example
>> [& code]
>> `(let [rcode# ~(reverse code)
>> fn# (to-fn rcode#)]
>> (run-example fn#)))
>
> Thanks for the complete example, it really helps.
>
> Macroexpand might help you see at least one of the problems:
>
> (clojure.core/let [rcode__614__auto__ ((printf "EXAMPLE2\n") (printf
> "EXAMPLE1\n"))
> fn__615__auto__ (user/to-fn rcode__614__auto__)]
> (user/run-example fn__615__auto__))
>
> Since (printf ...) returns nil, it looks like you'll be trying to bind
> rcode# to the value of (nil nil), that is 'nil' called with a single
> argument of 'nil'. It actually errors out before it gets that far,
> but anyway...
>
> Try completing as much of your manipulation as is possible outside the
> syntax-quote:
>
> (defmacro example [& code]
> (let [rcode (reverse code)]
> `(let [func# (to-fn ~rcode)]
> (run-example func#))))
>
> Also, try to avoid using builtin names like 'fn' for your own locals.
> It only leads to more pain in the long run.
>
> --Chouser
>
> >
>
--
Howard M. Lewis Ship
Creator Apache Tapestry and Apache HiveMind
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