Does this clarify the point I was making?
When writing macros, you cannot dynamically build one of the syntactic
sugar forms. For example, you cannot write a macro that expands cls
and member into (cls/member):
(defmacro call-static [cls member] `(~cls/~member))
-> java.lang.Exception: Invalid token: cls
Instead, you should build normal, unsugared forms:
(defmacro call-static [cls member] `(. ~cls ~member))
-> nil
>
> On Tue, Feb 3, 2009 at 11:26 AM, Mark Volkmann
> <r.mark.volkm...@gmail.com> wrote:
>>
>> Now I remember what I was thinking about. This isn't so much a
>> difference between macros and functions as it is a rule about
>> something you cannot do in a macro. Quoting from "Programming
>> Clojure"
>> ...
>>
>> "You cannot write a macro that expands to any of the syntactic sugar
>> forms ... For example, you cannot write a macro that
>> expands to (Math/PI)."
>
> Hm...
>
> (defmacro pi [] 'Math/PI) ==> #'user/pi
> (macroexpand '(pi)) ==> Math/PI
> (pi) ==> 3.141592653589793
>
> (defmacro strlen [s] `(.length ~s)) ==> #'user/strlen
> (strlen "hello") ==> 5
>
> (defmacro mydoc [s] `(:doc ^#'~s)) ==> #'user/mydoc
> (macroexpand '(mydoc doc)) ==> (:doc (clojure.core/meta (var doc)))
> (mydoc doc) ==> "Prints documentation for a var or special form
> given its name"
>
> That's a whole lot of sugar that all seems to work ok. Is there some
> other syntactic sugar form that does not work? Perhaps he's referring
> to actually producing reader macro usages, like this:
>
> (defmacro mydoc2 [s] `(:doc ~(symbol (str "^#'" s)))) ==> #'user/
> mydoc2
> (macroexpand '(mydoc2 doc)) ==> (:doc ^#'doc)
> (mydoc2 doc) ==> java.lang.Exception: Unable to resolve symbol:
> ^#'doc
>
> --Chouser
>
> >
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