2015-06-24 1:25 GMT+02:00 Ben Wolfson <wolf...@gmail.com>: > On Tue, Jun 23, 2015 at 4:17 PM, Ghadi Shayban <gshay...@gmail.com> wrote: > >> >> Tangentially: >> (remove even?) >> Will be faster than >> (remove (fn [i] (even? i))) >> because in the first case the dereference of the var 'even?' happens only >> once and the value inside the var will be passed to `remove` at the >> outset. In the second example the var dereference happens for every single >> item (though it's very cheap). The second example is equivalent to writing >> (remove >> #'even?) >> > > I can't seem to observe a difference between the two cases. >
A simple var reference like even? compiles to a fetch of its root val: @#'even? In the first case, that happens only once, passing the resulting fn object to remove. In the second case, the deref happens every time the fn is called, thus allowing for redefinition of even?. Have you ever passed passed #'handler to a server-start function (e.g. in a ring app), so that you might redefine the handler fn during run time of the server? Ad. thread topic: As detailed, clojure's evaluation semantics already help with transducers. Even better: Built transducer stacks should be pretty accessible to the JIT, since they contain no more var references (in the wiring). Also, since transducers are a kind of lexically closed pipe from input effect to output effect, hotspot's escape analysis should also kick in nicely. -- 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/d/optout.
