On 7/11/11 11:40 AM, Timothy Washington wrote:
Note: This message was originally posted by ' Shantanu' on the "*/Re:
Clojure for large programs/*" thread.
I took a look at Shantanu's macros, and I like the concept a lot. But
I would prefer something baked into the :pre condition itself. The
reason is that it just removes a layer of indirection. If you dig into
'*clj/clojure/core.clj*', you can see that the 'fn' macro is using
'assert' to test these conditions. Assert allows error messages to be
applied, ie:
/user => (assert false) /
/user => (assert false "fubar") /
However, (defmacro fn ...) assumes that just the boolean condition is
being passed in, A). But I'd like to have the option to pass in a
message B).
/A) /
/(def fubar /
/ (fn []/
/ {:pre [ *(true? false)* ] }/
/ (println "Hello World")))/
/(fubar)/
/
/
/B) /
/(def thing /
/ (fn []/
/ {:pre [ *[(true? false) "A false message"]* ] }/
/ (println "Hello World")))/
/(thing)/
I reworked the 'fn' macro, only for the :pre condition, as a
demonstration (see here <http://pastebin.com/fETV1ejJ>). The calling
semantics don't change that much. Is there any interest in putting
this into core? I'd use Shantanu's workaround otherwise, or in the
interim.
Thanks
Tim Washington
twash...@gmail.com <mailto:twash...@gmail.com>
416.843.9060
I'd like to see something like this added as well since I sometimes
write a comment by conditions to help remind myself of why they are
present. One comment on the patch that is probably obvious, but if we
change the API for :pre we would want to update the :post API as well to
keep them consistent.
-Ben
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