no need to use macros at all: (defn foo "creates a symbol named s with the value s in the current namespace " [s] (intern *ns* (symbol s) s))
that is, assuming I got the use case right. --Robert McIntyre On Wed, Dec 15, 2010 at 8:00 AM, Laurent PETIT <laurent.pe...@gmail.com> wrote: > 2010/12/15 Emeka <emekami...@gmail.com> >> >> Helllo All, >> Is there a better way of doing this? >> (defmacro foo [string] (let[b# string f# (symbol b#)] `(def ~f# ~b#))) > > Hello, > > What is it supposed to be used ? > > What do you expect the macroexpansion to look like ? > > As is stands, your example can go without the ending #'s since they aren't > declared inside the returned quoted expr. They're useless. > > So having > > (defmacro foo [string] (let [b string f (symbol string)] `(def ~f ~b))) > > But now, string is not (as you may think) evaluated within the let in the > macro. string is just an immutable datastructure containing "as is" what has > been passed to foo. So if what you pass to foo is something which > "evaluates" to a string, for example a string concatenation expression as > (str "the-" "value"), then the code will not do what it suggests it's doing > : > > user=> (defmacro foo [string] (let[b# string f# (symbol b#)] `(def ~f# > ~b#))) > #'user/foo > user=> (foo (str "the-" "value")) > java.lang.ClassCastException: clojure.lang.PersistentList cannot be cast to > java.lang.String (NO_SOURCE_FILE:0) > user=> (macroexpand '(foo (str "the-" "value"))) > java.lang.ClassCastException: clojure.lang.PersistentList cannot be cast to > java.lang.String (NO_SOURCE_FILE:0) > user=> > > > Now, if you just want the macro to take literal strings as input, then the > code can be further simplified to : > > (defmacro foo [string] `(def ~(symbol string) ~string)) > > user=> (defmacro foo [string] `(def ~(symbol string) ~string)) > #'user/foo > user=> (foo "the-string") > #'user/the-string > user=> the-string > "the-string" > user=> (macroexpand '(foo "the-string")) > (def the-string "the-string") > user=> > > HTH, > > -- > Laurent > > -- > 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
