Thanks Rich, Expanding into the symbol is clever, but less readable (IMO) than just expanding into the . form. Anyway, I get it now.
Stuart > On Feb 15, 2009, at 9:06 AM, Stuart Halloway wrote: > >> >> Does this clarify the point I was making? >> >> When writing macros, you cannot dynamically build one of the >> syntactic >> sugar forms. For example, you cannot write a macro that expands cls >> and member into (cls/member): >> >> (defmacro call-static [cls member] `(~cls/~member)) >> -> java.lang.Exception: Invalid token: cls >> >> Instead, you should build normal, unsugared forms: >> >> (defmacro call-static [cls member] `(. ~cls ~member)) >> -> nil > > > First off, 'sugared forms' is too imprecise to talk about. More > precise is, you can't write a macro that expands into a reader macro, > because reading is finished. But that is not the case here. Again, > start with, what do I want to write, and what expansion do I want? > > I want to write: > > (call-static foo bar) > > I want it to expand into: > > (foo/bar) > > Note the expansion does not contain any reader macros, so you can do > it. It is also important not to lose track of the data structures (not > strings!) you are manipulating. The expansion above is a list with one > (namespace-qualified) symbol in it. You can't get a namespace- > qualified symbol by putting two symbols on either side of a / , > instead: > > (defmacro call-static [cls member] > `(~(symbol (str cls) (str member)))) > > (macroexpand '(call-static foo bar)) > (foo/bar) > > (call-static System nanoTime) > -> 1234708658498938000 > > Rich > > > > > --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
