Re: get keys from defrecord
On Mon, Aug 29, 2011 at 10:14 PM, Steve Miner wrote: > > On Aug 29, 2011, at 8:20 PM, Alex Miller wrote: > >> I'm not sure if there are any enhancements in the 1.3 record support >> for this feature. > > > In 1.3beta2, the record class has a static method getBasis that will give you > the fields. I remember Fogus mentioning this on the mailing list. The > design notes [1] say "These methods should not be used in Clojure code" as > they're intended for tool support, but they seem generally useful to me. In a Lisp, anything useful for "tool support" and accessible from inside the language tends to be useful sometimes in macros as well; perhaps macros need to be considered part of "tool support" for a Lisp. After all, they are used to extend and metaprogram the language. -- Protege: What is this seething mass of parentheses?! Master: Your father's Lisp REPL. This is the language of a true hacker. Not as clumsy or random as C++; a language for a more civilized age. -- 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: get keys from defrecord
On Aug 29, 2011, at 8:20 PM, Alex Miller wrote: > I'm not sure if there are any enhancements in the 1.3 record support > for this feature. In 1.3beta2, the record class has a static method getBasis that will give you the fields. I remember Fogus mentioning this on the mailing list. The design notes [1] say "These methods should not be used in Clojure code" as they're intended for tool support, but they seem generally useful to me. user=> (clojure-version) "1.3.0-beta2" user=> (defrecord MyRecord [a b]) user.MyRecord user=> (MyRecord/getBasis) [a b] [1] http://dev.clojure.org/display/design/defrecord+improvements Steve Miner -- 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: get keys from defrecord
On Aug 29, 2011, at 2:57 PM, Tassilo Horn wrote: > > I guess the problem with that is that you need to have an instance of > the record before you can use `keys'. And to create an instance, at > least you have to know the number of keys. > > However, you can inspect the record's constructor using reflection: Or, if structs will do for your application, then you can do this more simply: user=> (defstruct mystruct :a :b :c) #'user/mystruct user=> (keys (struct-map mystruct)) (:a :b :c) -Lee -- 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: get keys from defrecord
There is no good way to do this in 1.2 other than using the instance mechanism that Aaron suggests. I have had this need myself for several meta-programming type use cases (building specialized record serializers, universal record constructors, etc). We wrap defrecord in our own macros that generate multimethod implementations at record construction time. One possible solution is to use Java reflection to grab the fields directly. Clojure generates some in the class, but I think they all start with an _, so you skip those and probably come up with the correct fields. However, I presume the names would be mangled and you'd need to de-mangle them. I'm not sure if there are any enhancements in the 1.3 record support for this feature. On Aug 29, 11:54 am, Razvan Rotaru wrote: > Hi, > > Assuming I have: > > (defrecord myrecord [:a :b :c]) > > is there a way to get the list of keys from the record definition? > > Thanks, > Razvan -- 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: get keys from defrecord
Hi, it could help if you can provide more info on what you're trying to achieve 2011/8/29 Razvan Rotaru > Hi, > > Assuming I have: > > (defrecord myrecord [:a :b :c]) > > is there a way to get the list of keys from the record definition? > > Thanks, > Razvan > > -- > 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 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: get keys from defrecord
Aaron Bedra writes: > user=> (defrecord MyRecord [a b c]) > user.MyRecord > user=> (def rec (user.MyRecord. "one" "two" "three")) > #'user/rec > user=> (keys rec) > (:a :b :c) I guess the problem with that is that you need to have an instance of the record before you can use `keys'. And to create an instance, at least you have to know the number of keys. However, you can inspect the record's constructor using reflection: (-> MyRecord .getConstructors first .getParameterTypes) This gets you an array of the record's parameter types. It seems, that the last 2 Object parameters are some internal stuff (metadata?), so the array length - 2 is the arity. (-> MyRecord .getConstructors first .getParameterTypes) ==> 5 ;; so the record has 3 keys If the record doesn't have fields hinted with primitive types, then that's enough knowledge to create an instance. If there are primitive type hints, then the constructor has primitive type parameters you have to match when calling it. All in all, it seems there's everything you need to create a function that creates a dummy instance of arbitrary (unknown) records that you can query for its keys afterwards. But maybe there's a better way... :-) Bye, Tassilo > On 08/29/2011 12:54 PM, Razvan Rotaru wrote: >> Hi, >> >> Assuming I have: >> >> (defrecord myrecord [:a :b :c]) >> >> is there a way to get the list of keys from the record definition? >> >> Thanks, >> Razvan >> -- 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: get keys from defrecord
user=> (defrecord MyRecord [a b c]) user.MyRecord user=> (def rec (user.MyRecord. "one" "two" "three")) #'user/rec user=> (keys rec) (:a :b :c) Cheers, Aaron Bedra -- Clojure/core http://clojure.com On 08/29/2011 12:54 PM, Razvan Rotaru wrote: Hi, Assuming I have: (defrecord myrecord [:a :b :c]) is there a way to get the list of keys from the record definition? Thanks, Razvan -- 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
