On Wed, Dec 09, 2009 at 02:35:24PM -0800, Joost wrote: > On 9 dec, 17:03, Jeff Dik <s45...@gmail.com> wrote: > > The part "Running code at read-time lets users reprogram Lisp's > > syntax" caught my attention. Is this talking about reader macros? I > > believe I read that clojure doesn't have reader macros, so would it be > > more accurate to say "The whole language is there, _most_ of the > > time"? > > Clojure doesn't have user-implementable reader macros, but neither > does emacs lisp. Reader macros are nice when you need to embed a > significantly different looking kind of language - that's why clojure > implements regular expressions as a reader macro instead of a function > on a string; you'd have to doubly escape every backslash otherwise. > But they're mostly "only" a way to provide syntactic sugar. > > I think what Paul is +mainly+ talking about in terms of "syntax" is > just plain ordinary macros that can implement short-circuiting and > different evalution strategies for readable data, so that you can > implement things like (unless ...) yourself, with no (significant) > overhead compared to the built in (if), but you'll have to keep to the > basic reader constructs (but not evalution rules). This has the > advantage of keeping the language simpler to parse and readble for > humans too. > > The other part of the "always there" is that you can use whatever is > already compiled/parsed to construct new macros, so you can build > macros on top of each other, and on top of a mix of macros and (user- > defined) functions instead of being restricted to the "traditional" > sparseness of C preprocessor macros.
Thanks to everyone who replied to my question! I had not realized that clojure had built-in reader macros (which I should have realized from section 2.2 "Reader Macros" of "Programming Clojure"). The day I wrote the original email was the first day I think I actually realized what reader macros do, which, in retrospect, should have been obvious from their name. Just another example of Lisp blowing my mind. I wasn't advocating user-creatable reader macros or bemoaning the lack of them in Clojure. I trust Rich Hickey's judgment :-) He's much smarter than me and is an excellent language designer[1] (IMHO). Still, I may have to play with user-creatable reader macros in Scheme or Common Lisp. I can see how they could make code harder to read if a lot of people used them, but wonder if people standardized on some of them, if they might make it more easier to write code for certain fields (e.g. matrix math). I think Graham Fawcett's idea of having an experimental branch of Clojure that allowed user-creatable reader macros is a good idea and wish I was smart enough to do it :-) Thanks, Jeff [1]: Side note. I think one of the best illustration's of Rich's genius[2] is that he was able to combine Lisp, Java, functional programming, and concurrency into such a beautiful language, as opposed to Bjarne Stroustrup (also extremely smart) taking C and adding OOP, etc, and making a lot of very reasonable decisions, and still coming up with a monstrosity. [2]: Side note on the side note. Another example of Rich's genius are the changes to Clojure for version 1.1. > > -- > 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
