Re: delays are forced by deref too early?
On Mon, Sep 21, 2009 at 6:48 PM, patrickdlogan wrote: > > > (force del) ; note that @del would be equivalent here > > This is at the core of my question. I did not understand that a delay > is something that can be deref'd until I read the source. > Well, it's documented but not on #'delay: => (doc deref) - clojure.core/deref ([ref]) Also reader macro: @ref/@agent/@var/@atom/@delay/@future. Within a transaction, returns the in-transaction-value of ref, else returns the most-recently-committed value of ref. When applied to a var, agent or atom, returns its current state. When applied to a delay, forces it if not already forced. When applied to a future, will block if computation not complete I'll open a ticket for changing the docstring of delay to mention deref/@. Christophe -- Professional: http://cgrand.net/ (fr) On Clojure: http://clj-me.blogspot.com/ (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 -~--~~~~--~~--~--~---
Re: delays are forced by deref too early?
> (force del) ; note that @del would be equivalent here This is at the core of my question. I did not understand that a delay is something that can be deref'd until I read the source. Knowing now that a delay does behave this way, I can work with it as such. Given the doc string for delay, I wasn't sure whether this was accidental behavior due to the implementation, or by design. Thanks --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
Re: delays are forced by deref too early?
Hi Patrick, If that really annoys you, you can tell the repl to display Delay instances as dumb objects: (defmethod print-method clojure.lang.Delay [x w] ((get-method print-method Object) x w)) user=> (defmethod print-method clojure.lang.Delay [x w] ((get-method print-method Object) x w)) # user=> (def del (delay (println "printed") (+ 2 3))) #'net.cgrand.parsley/del user=> del # user=> (force del) ; note that @del would be equivalent here printed 5 Christophe On Mon, Sep 21, 2009 at 5:53 PM, patrickdlogan wrote: > > I expected a delay only to be forced by an explicit call to force. > instead it looks like, being a kind of IDeref, a delay will be forced > by the REPL. > > e.g. > > user=> (def del (delay (println "printed") (+ 2 3))) > #'user/del > user=> del > printed > # > user=> (force del) > 5 > > The documentation seems to imply the only way to force a delay is > through the force procedure... > > " Takes a body of expressions and yields a Delay object that will > invoke the body only the first time it is forced (with force), and > will cache the result and return it on all subsequent force > calls." > > > > -- Professional: http://cgrand.net/ (fr) On Clojure: http://clj-me.blogspot.com/ (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 -~--~~~~--~~--~--~---
Re: delays are forced by deref too early?
On Sep 21, 6:53 pm, patrickdlogan wrote: > I expected a delay only to be forced by an explicit call to force. > instead it looks like, being a kind of IDeref, a delay will be forced > by the REPL. > > e.g. > > user=> (def del (delay (println "printed") (+ 2 3))) > #'user/del > user=> del > printed > # > user=> (force del) > 5 > > The documentation seems to imply the only way to force a delay is > through the force procedure... I'm pretty sure force is still causing the evaluation... Just indirectly :) The delay here is forced by its print method, which, as you can see, also prints the value. Delays could be changed to print something like #, but I wonder if that's really useful. --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
delays are forced by deref too early?
I expected a delay only to be forced by an explicit call to force. instead it looks like, being a kind of IDeref, a delay will be forced by the REPL. e.g. user=> (def del (delay (println "printed") (+ 2 3))) #'user/del user=> del printed # user=> (force del) 5 The documentation seems to imply the only way to force a delay is through the force procedure... " Takes a body of expressions and yields a Delay object that will invoke the body only the first time it is forced (with force), and will cache the result and return it on all subsequent force calls." --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
