On Fri, Jan 1, 2016 at 9:53 PM, William la Forge <laforg...@gmail.com>
wrote:
> Andrey,
>
> This is where I have a problem. Ii could have implemented dewdrop lenses
> as functions that could be composed. But the code would be harder to
> understand and possibly be slower. I just do not see the point.
>
I agree with your main argument, but I don't know how using records makes
thinks more easy understandable in this concrete case and how using
functions over records will make code slower. Transducers has a performance
improvements over classical transformation compositions, and in this case,
the cats lenses leverage the same technique.
>
> Implementing dewdrop lenses as records makes it dirt simple for anyone to
> create more kinds of lenses. And the ladd function to create a new record
> with the composed getter and setter functions is pretty clean as well.
>
Yes but it implies more api to know, that is not bad but if you limit the
set of new api that one should learn/use, will contribute to more familiar
and easy api. Adding new api also implies more time to understand it and
remember when it should be used.
>
> Isn't it more important to have code you can analyze easily, and which
> even a novice clojurist like myself can embrace and enhance a whole lot
> more important than being able to say that we can use comp to compose these
> lenses???
>
Yes, I agree with you, the code readability is very very important. But
this concrete case I don't found big differences in code readability:
;; dewdrop
(defn key-lens [k]
(lens.
(fn [d] (get d k))
(fn [d v] (assoc d k v))))
;; cats
(defn key
[k]
(lens
(fn [s] (get s k))
(fn [s f] (update s k f))))
The code is mostly the same...
> I see good engineering as leveraging computer science so the programming
> grunts can make effective use of it. Programming is real grunt work, after
> all. No matter how much you dress it up, we all needs must get our hands
> dirty and put our backs into it.
>
My two cents.
Andrey
>
> Bill
>
> On Friday, January 1, 2016 at 9:09:08 AM UTC-5, Andrey Antukh wrote:
>>
>> Hi!
>>
>> I have read the readme and I don't found a big evidence of something
>> wrong so, nice work!
>> Furthermore, do you know about https://github.com/funcool/cats ? It has
>> a lens and traversable implementation for clj/cljs. You can read the
>> related documentation here: http://funcool.github.io/cats/latest/#lens .
>>
>> You can found that lenses, using cats approach, are working just like
>> transducers (function composition), you do not need any special function
>> for combine lenses, just use comp. One of the readme examples (from your
>> repository) that combines two lenses, in cats can be written in this way:
>>
>> (require '[cats.labs.lens :as l])
>> (def xy-lens (comp (l/key :x) (l/key :y))
>> ;; Or just use (l/in [:x :y])
>>
>> (l/focus xy-lens {:x {:y 1}})
>> ;; => 1
>> (l/over xy-lens inc {:x {:y 1}})
>> ;; => {:x {:y 2}}
>>
>> Happy new year!
>> Andrey
>>
>> On Fri, Jan 1, 2016 at 2:54 PM, William la Forge <lafo...@gmail.com>
>> wrote:
>>
>>> I've been looking at lenses and while it looks pretty simple and very
>>> useful, I had a hard time getting it. So I came up with my own take on
>>> lenses. https://github.com/laforge49/dewdrop#readme
>>>
>>> So perhaps I still do not understand lenses and what I've done is wrong.
>>> Or perhaps having been through the exercise I'm now getting it and what
>>> I've done is no simpler than what everyone else has done. Or perhaps I've
>>> just described things with fewer technical terms.
>>>
>>> So I'd appreciate it if you would review this very short document and
>>> tell me what I don't understand. Or that I've actually done something
>>> worthwhile with lenses???
>>>
>>> Thanks!
>>> Bill
>>>
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>>
>>
>>
>> --
>> Andrey Antukh - Андрей Антух - <ni...@niwi.nz>
>> http://www.niwi.nz
>> https://github.com/niwinz
>>
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--
Andrey Antukh - Андрей Антух - <n...@niwi.nz>
http://www.niwi.nz
https://github.com/niwinz
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