Hi Hugh, I don't see how this would work in general, which is why a I suggested a special-purpose macro before. Surely you would not want a binding to force all sequences while that binding is in effect. And if not that, what would the general strategy be for deciding which sequences to force, and which not?
Stuart > On Tue, Jan 20, 2009 at 12:53 AM, Timothy Pratley > <timothyprat...@gmail.com> wrote: >> >> >>> How would one go about fixing f1 (or b1)? >> >> Depends what you want to achieve... here are two possible 'fixes': >> >> ; don't use lazy evaluation >> (defn f1 [] >> (doall (map (fn [x] *num* ) [1]))) >> >> ; use lazy evaluation, but preserve the binding when the lazy >> sequence >> is created >> (defn f1 [] >> (let [mynum *num*] >> (map (fn [x] mynum) [1]))) >> >> > > Yes, these work. They presume the author of f1 knows that the caller > is liable to rebind *num*. > > Is it always going to be unsafe to use Vars in a lazily evaluated > function? If so, could the compiler or runtime automate forcing doall > or let? > > I'm understanding better. The caller can also do > > (binding [*num* 1024] (doall (f1))) > > The caller doesn't necessarily know he's getting a lazy sequence back, > but this would be a boilerplate pattern you use anytime you use > binding. Again, could/should Clojure automate doing that? > > > Thanks all for the insights. > > Hugh > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
