On Jul 22, 2012, at 7:42 PM, Warren Lynn wrote: > I plan to change all my major data structures to records instead of plain > maps. Since record has everything a map provides, I figure there won't be any > harm. But is that really so? Would appreciate the opinions from people who > know better.
I know I'm in the minority but I happen to prefer maps to records, and in fact I really like struct-maps which I gather may (?) not be long for this world. Nonetheless, since you asked, following are two old messages in which I attempted to point out some of the things that I like about struct-maps as opposed to records. ------------------ On Jul 28, 2011, at 8:19 PM, Alex Osborne wrote: > The main use cases for the old structs feature on the other hand are > completely replaced by records and it is recommended that new code use > defrecord instead of defstruct. I had some code using structs and, following advice like this, replaced it with code using records. The result was more complicated, uglier and not noticeably faster. I reverted to the struct version. I like structs, and I hope they are retained! -Lee PS for anyone who is curious the struct version of the code in question is as follows (with push-types having a value like '(:exec :integer :float :code :boolean :auxiliary :tag :zip)): (defmacro define-push-state-structure [] `(defstruct push-state ~@push-types)) (define-push-state-structure) (defn make-push-state "Returns an empty push state." [] (struct-map push-state)) The record version that I came up with is: (defn keyword->symbol [kwd] "Returns the symbol obtained by removing the : from a keyword." (read-string (name kwd))) (defmacro define-push-state-record-type [] "Defines the pushstate record type. The odd trick with read-string was a hack to avoid namespace qualification on the pushstate symbol." `(defrecord ~(read-string "pushstate") [~@(map keyword->symbol push-types)])) (define-push-state-record-type) (defmacro make-push-state "Returns an empty push state." [] `(pushstate. ~@(map (fn [_] nil) push-types))) Maybe there's a better way -- I wouldn't doubt it -- but the struct version was simple and worked exactly like I wanted it to, so I decided to stop tinkering. ----------------- 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 ---------------------- On Jan 18, 2011, at 7:21 PM, Chas Emerick wrote: > You might find my minor sugar for defining records whose slots have default > values: > > http://cemerick.com/2010/08/02/defrecord-slot-defaults/ Nice -- I do think it'd be good for something like this to be built in. > Also worth noting is the further enhancement by Michael Fogus (linked to in > the comments on the above post) that adds support for kwargs to the factory > function for the defined record. Oh yes, keyword args are another nice thing about struct-map that I'd forgotten about but which have also been important to me in some contexts, e.g. when there are lots of args. > I also like a few aspects of what structmaps provide vs. regular maps (in > particular, documentation of intent), but records have too many far more > significant advantages and are too easy to add sugar to to reclaim the minor > bits structmaps offer to not use IMO. If the above conveniences get baked in then I'll probably agree. ---------------------- -- 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
