And that's ok, there's obviously more to it and not knowing or
understanding the spec I wouldn't expect you to make sense of that piece.
Still, the question really is: If you were to do this, would you implement
deftype, gen-class instead? Would the hacked approach be a bad idea and if
so for what reason? Staying within the bounds of the question are there
other approaches to doing the same thing? I initially just wanted to use
with-meta that could attach to any data, but obviously with-meta limits
what it can be attached to which led to the above approach.
Thanks,
On Thursday, December 12, 2013 10:43:22 AM UTC-5, James Reeves wrote:
>
> Why not something like:
>
> {:where [[:id 'identity]] :sort [[:id :desc]]}
>
> That would make it relatively straightforward to merge queries (use `into`
> and then check for duplicates in :sort).
>
> To me, it doesn't make a huge amount of sense to tie sorting logic onto
> the field itself.
>
> - James
>
>
> On 12 December 2013 13:56, Tim <[email protected] <javascript:>> wrote:
>
>> Hi James,
>>
>> I'm not basing logic on types alone. That aside, here's an example to
>> highlight the specific problem:
>>
>> {:where [:id 'identity]}
>>
>> Here are two options for sorting by id:
>>
>> 1. {:where [:id 'identity] :sort-by :id :sort '>}
>>
>> 2. {:where [:id (object 'identity {:sort >})}
>>
>> I chose #2, which is immensely helpful when constructing multi-sort
>> queries. I can understand how #2 may raise some eyebrows/questions from a
>> query logic perspective, but I am trying to reduce the scope down to
>> question at hand and not get into unraveling the entire spec.
>>
>> Does that help? & Thanks.
>>
>> On Thursday, December 12, 2013 7:59:26 AM UTC-5, James Reeves wrote:
>>
>>> 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 <[email protected]> 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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>>>
>>>
>
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