On Wednesday, March 13, 2013 2:46:06 PM UTC-7, puzzler wrote: > On Wed, Mar 13, 2013 at 2:06 PM, Marko Topolnik > <marko.t...@gmail.com<javascript:> > > wrote: > > >> As far as I understand it, *set!* modifies the *thread-local* binding, >> just like the *binding* macro, but doesn't delimit a definite scope of >> validity for the binding. You can *set!* any dynamic var with the same >> semantics. >> > > You can't just set! any dynamic var, you can only set! vars that are both > dynamic *and* have been bound again with the binding construct. > > => (def ^:dynamic a 2) > #'user/a > => (set! a 3) > IllegalStateException Can't change/establish root binding of: a with set > clojure.lang.Var.set (Var.java:233) > => (binding [a 1] (set! a 3)) > 3 > > > This is why I'm puzzled about how things like (set! *unchecked-math* true) > are handled. Clearly, in this special case you can use set! without first > calling binding. >
Not really a special case, although I suppose you could argue it either way. These vars, too, must be bound before being set!. But the code that binds them is in the compiler: https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/Compile.java#L72 binds *unchecked-math* *warn-on-reflection* before it starts compiling files. The only way you could make your own vars be set!able is to use them inside a context in which they've already been bound; for example, you could define a (let-me-set-stuff &body) macro and evaluate the user's code in that context. That's basically the same as how the compiler and the repl work: they run all of your code in a context where bindings are established. -- -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
