Thinking about it again, Is qualifying this as a non-bug, a known limitation the best that can be said about it ?
Could the implementation be improved to handle this case, or is there a theoretical reason I've not thought about that prevents doing this for the general case ? Thanks, -- Laurent 2009/4/24 Christophe Grand <christo...@cgrand.net>: > > Hi Kevin! > > Your (let [dummy 0] ...) is a single expression and, as such, is entirely > compiled before being executed. > But to properly compile (add 1 (mul magic x)) 'add need to have a value and > it will not have a value until the (compiled) expression is executed. > So, for this expression, its compilation depends on its execution that > requires its compilation... > > Thus a macro can on only be used in subsequent op-level expression, not in > its own. > > I just learnt this lesson again: > http://clj-me.blogspot.com/2009/04/vicious-bug.html > > hth, > > Christophe > > ke...@ksvanhorn.com a écrit : >> I have more information on this now, and it is definitely a bug in >> Clojure -- defmacro within a let doesn't work correctly. Consider the >> following file: >> >> --- BEGIN foo1a.coj --- >> (ns com.ksvanhorn.foo1a) >> >> (let [dummy 0] >> (defmacro add [& args] `(unchecked-add ~...@args)) >> (defmacro mul [& args] `(unchecked-multiply ~...@args)) >> (let [magic 1812433253 >> x 5489 >> v (add 1 (mul magic x))] >> (println (str "v: " v)))) >> --- END --- >> >> If I type "(use 'com.ksvanhorn.foo1a)" at the REPL, I get >> >> v: (clojure.core/unchecked-add 1 (clojure.core/unchecked-multiply >> 1812433253 5489)) >> >> printed out and nil returned, but if I just type >> >> (uncheck-add 1 (unchecked-multiply 1812433253 5489)) >> >> I get 1301868182. >> >> Although in this case the defmacro doesn't need to be inside the let, >> I actually have a real need for doing defmacro inside a let -- I have >> a computed constant that I want to use in several places, and one of >> those places is in the macro definition. >> >> > >> >> > > > -- > Professional: http://cgrand.net/ (fr) > On Clojure: http://clj-me.blogspot.com/ (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 -~----------~----~----~----~------~----~------~--~---
