I was looking for it, but to no avail! Anyway, something I was wondering about. Why don't we take the best from all possible worlds? In this case, Clojure and Scheme (R6RS). It would be nice to have syntax-quote, unquote, and unquote-splicing as true macros (or special forms), and keep `, ~, and ~@ (and of course auto-gensyms) as convenient reader shortcuts. Just seems more elegant, plus it let's you do things like building arbitrary syntax-quote expressions with Lisp itself (lispier, heh?). Now, who would go to such extremes? ... well, you never know :)
But, something more important! Why not adopt R6RS's expansion rules for syntax-quotes? This is something that was hinted at even in the Common Lisp specs, the only problem being that, at the time, Scheme didn't entirely get it right when it came to the distributive application of unquote applied to an unquote-splicing in a nested syntax-quote (backquote): Example ------------- (def a 2) (def b 3) (def c 5) (def x `(a b c)) ``(~...@x) ---> `(~user/a ~user/b ~user/c) and finally to: (2 3 5) But R6RS finally got it right, and now (unquote a1 a2 a3 ...) really does what it should, so you get the exact same behavior. R6RS defines the nested syntax-quote expansion like so: "Quasiquote forms may be nested. Substitutions are made only for unquoted components appearing at the same nesting level as the outermost quasiquote. The nesting level increases by one inside each successive quasiquotation, and decreases by one inside each unquotation." This is, curiously, more or less how Paul Graham puts it for Common Lisp in his ANSI Common Lisp book. And, by the way, I've noticed that SBCL employs this exact rule when expanding backquotes. The upshot (among other things) for Clojure is that, if Rich likes the idea, we would finally get a decent, human-understandable, expansion of syntax-quote forms as well. Compare the above: ``(~...@x) ---> (clojure.core/seq (clojure.core/concat (clojure.core/ list user/a user/b user/c))) to this: ``(~...@x) ---> `(~user/a ~user/b ~user/c) or, at most: ``(~...@x) ---> (syntax-quote ((unquote user/a) (unquote user/b) (unquote user/c))) And that was a really simple nested syntax-quote. I wouldn't even want to try tackling more complex ones. Anyway, just an idea. Rock -- 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
