Indeed ! I was stuck in the macro thinking, thanks for getting us out of it !
And then this solution not only works for literal strings: user=> (foo (str "yo" "man")) #'user/yoman user=> yoman "yoman" user=> 2010/12/16 Robert McIntyre <r...@mit.edu> > 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<clojure%2bunsubscr...@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<clojure%2bunsubscr...@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
