For nested backquotes, Paul Graham in ANSI Common Lisp gives the clearest explanation. He makes it look almost trivial. As a matter of fact, once you get the hang of it, it's not at all that complicated.
I've pretty much verified that what he says concerning CL backquotes applies perfectly to Clojure as well. The only difference is that you have to remember that in Clojure, backquotes can *resolve* unqualified symbols too (which is actually powerful and cool). So no problem there. Rock On Aug 11, 6:00 pm, Jonathan Smith <jonathansmith...@gmail.com> wrote: > For the sake of contradicting myself, in this paper Alan Bawden > explains quasi-quote much better than I can. > > https://eprints.kfupm.edu.sa/60346/1/60346.pdf > > Note the explanation towards the end of defmacro and constructs such > as ',' (in clojure I believe it would be '~' ) > > Also note that Clojure has the added wrinkle of namespace > qualification. > > On Aug 11, 1:31 am, Jonathan Smith <jonathansmith...@gmail.com> wrote: > > > On Aug 10, 3:20 pm, Dragan Djuric <draga...@gmail.com> wrote: > > > > For example: > > > > (defmacro creator [param] > > > `(defmacro created [p] `(the code...)) ;; note the nested quote... > > > how to resolve that? any examples? > > > Although I wouldn't cite my own code as a necessarily *good* or easy > > to understand example, I'll pimp it anyway as it is written and > > already on the net... > > >http://github.com/JonathanSmith/CRIB/blob/89a3f4d9c797ef6f4e4f456001f... > > > A macro is exactly the same as a function, except it has special > > evaluation rules. > > You'll notice that in what I posted, I only use defmacro once, > > everything else is a function that returns a list > > > (I've found that this gives me extra flexibility later on when I want > > to continue extending the macro-metaphor... (or if I happen to want to > > do runtime definition of certain things, I can swap out the macro for > > a function call and an 'eval')). > > > You'll also notice that syntax quote qualifies every symbol that it is > > passed. > > Your particular example wouldn't work, because you can't define a name- > > space qualified symbol. There are two ways that you could circumvent > > this. > > 1.) use regular old list > > (list 'defmacro 'created ['p] `(code ...)) > > > 2a.) Escape and quote certain things: > > > `(defmacro ~'created [p#] `(code goes here..)) > > > or > > > 2b.) `(defmacro ~'created [p#] ~(fn-that-returns-your-code p# and > > probably some args and stuff)) > > > or > > > 2c.) > > (let [fn-that-generates-expansion > > (code-to-generate-a-fn-that-generates-an-expansion)] > > `(defmacro ~'created [p#] (~fn-that-generates-expansion p#))) > > > You don't actually need to use nested backquote* (For anything**, > > AFAIK), I tend to avoid it because I think it makes the code fairly > > unreadable (yes, more unreadable than what I posted). I normally use a > > helper function and pass the arguments (similar to a foo and foo-1 > > function when doing recursion). > > > --------------------- > > * backquote == syntaxquote > > > ** I think I used nested backquotes one time in common lisp for > > something, but I can't remember *why* it was necessary, in particular. > > I think it is the case where you want to pass a symbol from one macro- > > environment to the next, say generating a bunch of accessors... --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
