Scheme style macros in Clojure: https://github.com/qbg/syntax-rules
Scott On Sat, Dec 3, 2011 at 1:20 PM, Razvan Rotaru <razvan.rot...@gmail.com>wrote: > Hi everyone, > > I was searching the web these days trying to find out more about these > two macro systems and understand their differences, and why one is > preferable over the other (or not). I'd like to share with you some > ideas, and hopefully get some opinions back as well. Coming from the > lisp side, and without much knowledge on scheme macros, I'm also > trying to decide for myself whether scheme macros can have a > (practical) advantage. > > One good point (found here http://lambdagrok.wikidot.com/forum/t-194636) > I think explains it pretty well: lisp macros merely transform a list > into another, while scheme macros use a pattern matching "sub- > language" to "apply transformations" on the input syntax, and produce > new syntax. I think this puts the finger on the spot. > > It seems to me that with macros, scheme breaks out of the > homoiconicity of lisp, and opens up a new array of possibilities: > define new languages with <b>different</b> syntax (while lisp allows > new languages but with the same syntax). I'm saying this by looking at > Racket and the direction it has chosen to go (have a look at Typed > Scheme and Datalog). This looks like the world turned upside down: the > pattern matching macro system is the essence of the system, and scheme > is just another language defined with it. The list is not that > important anymore, since it's not so essential for the macro system. > > Now, I have read some opinions which say that most who choose the > scheme macros, make it for the pattern matching abilities and not for > the hygienic part. This seems like a reasonable thing to do, since I > don't hear lispers complain about unhygienicity. If there are people > out there who had some practical experience with scheme macros, I hope > they read this post and share some thoughts. > > I have a feeling that there's an additional gain with scheme macros: > debugging information given by the system when something goes wrong. > But it's only a feeling, I know too little of this subject to be sure. > Macros are hard to debug. The stacktrace displayed by clojure does not > contain information related to macro code. It's probably hard to do. > My feeling relates to the fact that in scheme macro processing is not > arbitrary, but rather strictly defined and under control. So I'm > thinking that this gives scheme more control over what's going on in a > macro and also enables scheme to give me more information in a > stacktrace. I'd love to hear other opinions on this. > > Another point I find peculiar is the small attention that scheme > macros got during all these years. I wonder why it's like that. It > could be scheme's low score for practical stuff, but then again I > don't know of another language that borrows these kind of macros. Does > anybody know? > > And lastly, a question to Rich Hickey, should he read this post: what > is the reasoning behind the choice of lisp macros over scheme's? > > Cheers, > Razvan > > -- > 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 -- 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
