It's hard to offer an opinion without some sense of the data structures you
are producing.
In the case of sorting by identifier, why do you need a new type? It sounds
like you're basing your logic on data types, rather than the data itself.
- James
On 12 December 2013 04:26, Tim <tcr1...@gmail.com> wrote:
> As an experiment, I've written a DSL that generates database queries using
> *effectively* only the data. The query logic is derived from the data
> assemblance and choice of data structures (or types). I am at the stage
> where I have all the logic working, and I am now moving into perf testing
> and tuning. BUT, before I do, there's this one hack I have implemented that
> has me asking the this question.
>
> As I wrote the DSL I ran out of data structure types to account for a few
> defined meanings within the query logic. As a short term hack I decided to
> attach meta data to symbols where the meta data contained a data value
> along with, for example, a sort option. I only intended for this to be
> short term until I got around to figuring out the semantics of Clojure's
> deftype or defrecord.
>
> Here's the hack:
>
> (defn object [v m]
> (let [id (gensym #"object#")]
> (with-meta id
> (merge m {:default v :id id}))))
>
>
> (defn object? [o]
> (if-let [it (meta o)]
> (if (= (it :id) o)
> true false)
> false))
>
> (defn inspect
> ([o]
> (inspect o nil))
> ([o & xs]
> (if-let [it (meta o)]
> (if (= (:id it) o)
> (if-let [x (first xs)]
> (if (coll? x)
> (select-keys it x)
> (x it))
> it)))))
>
> (defn instance
> ([o]
> (instance o nil))
> ([o & args]
> (if-let [it (meta o)]
> (if (= (:id it) o)
> (if-let [x (:default it)]
> (if (fn? x)
> (if-let [args (or (and (some identity args) args) (it
> :args))]
> (apply x args)
> (x))
> x)
> it)))))
>
>
> => (def o (object #(java.util.UUID/randomUUID){:sort '>})
> object#24397
>
> => (object? o))
> true
>
> => (instance o)
> #uuid "3c9cca8b-59e2-46b2-9175-468de3a21a22"
>
> => (inspect o :sort))
> >
>
> So now I've been reading up on Clojure's deftypes & defrecords and while
> it I expect they are both considered the right tool for the job,
> everything I read seems like overly complicated bloat code compared to my
> hack. Am I missing something? Is this a case where you wouldn't be caught
> dead using the above hack? Why or why not?
>
> As I see it: I'm not creating and/or holding millions of objects that
> would need to be shared, altered or held onto. These have relatively short
> lives that only serve in compiling to a different query language. Type
> hints or java interop really shouldn't matter.
>
> Notes:
>
> 1. While the above function names may carry OO concepts, these functions
> are not intended to fulfil all of them them; rather they only fill a
> specific functionality gap that appears to meet my needs.
> 2. I realize one wouldn't sort on a UUID, it's just an example to show the
> functionality. :)
>
>
> Thanks,
> Tim
>
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