On Sat, May 25, 2013 at 3:16 PM, Steven Degutis <sbdegu...@gmail.com> wrote:
>
> Also I just remembered, sometimes to solve the second one, I would do ((if
> condition transformer identity) obj) but that feels ugly.
>
but the condition has to contain obj, so obj is referred twice ? otherwise
i kinda like it
>
>
> On Sat, May 25, 2013 at 7:13 AM, Cedric Greevey <cgree...@gmail.com>wrote:
>
>> Seems to me that (merge {:attr something} obj) answers the OP's question,
>> mentions obj only once, and is short and pithy. OTOH it computes the
>> "something" every time, whether it's needed or not, so in cases where
>> "something" is expensive to compute (or has side effects that should only
>> happen if it winds up in the output!) then another method needs to be used.
>>
>>
>> On Sat, May 25, 2013 at 8:08 AM, atkaaz <atk...@gmail.com> wrote:
>>
>>> like:
>>> => (definline pred-transform [obj pred tf]
>>> `(let [o# ~obj]
>>> (if (~pred o#) o#
>>> (~tf o#))))
>>> #'cgws.notcore/pred-transform
>>>
>>> => (pred-transform (println 1) nil? #(println % "."))
>>> 1
>>> nil
>>> => (pred-transform (println 1) #(not (nil? %)) #(println % "."))
>>> 1
>>> nil .
>>> nil
>>>
>>>
>>> On Sat, May 25, 2013 at 3:07 PM, atkaaz <atk...@gmail.com> wrote:
>>>
>>>> in which case it does get evaluated twice if form:
>>>> => (pred-transform (println 1) #(not (nil? %)) #(println % "."))
>>>> 1
>>>> 1
>>>> nil .
>>>> nil
>>>>
>>>> => (pred-transform (println 1) nil? #(println % "."))
>>>> 1
>>>> 1
>>>> nil
>>>>
>>>> so maybe a let + gensym would be in order?
>>>>
>>>>
>>>>
>>>> On Sat, May 25, 2013 at 3:04 PM, atkaaz <atk...@gmail.com> wrote:
>>>>
>>>>> Shouldn't it be like:
>>>>>
>>>>> (definline pred-transform [obj pred tf]
>>>>> `(if (~pred ~obj) ~obj
>>>>> (~tf ~obj)))
>>>>> => (pred-transform 1 #(not (nil? %)) println)
>>>>> 1
>>>>> => (pred-transform 1 nil? println)
>>>>> 1
>>>>> nil
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Sat, May 25, 2013 at 2:55 PM, atkaaz <atk...@gmail.com> wrote:
>>>>>
>>>>>> just wondering if obj is a form does it get evaluated twice?
>>>>>>
>>>>>>
>>>>>> On Sat, May 25, 2013 at 2:51 PM, Jim - FooBar(); <
>>>>>> jimpil1...@gmail.com> wrote:
>>>>>>
>>>>>>> no need for macros... :)
>>>>>>>
>>>>>>> (definline safe-assoc [m k v]
>>>>>>> `(if (contains? ~m ~k) ~m
>>>>>>> (assoc ~m ~k ~v)))
>>>>>>>
>>>>>>> (definline pred-transform [obj pred tf]
>>>>>>> `(if ~(pred obj) ~obj
>>>>>>> ~(tf obj)))
>>>>>>>
>>>>>>> Jim
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 25/05/13 12:44, atkaaz wrote:
>>>>>>>
>>>>>>> may I see the macro for the latter, if you decide to go that way ?
>>>>>>> thx
>>>>>>>
>>>>>>>
>>>>>>> On Sat, May 25, 2013 at 2:24 PM, Steven Degutis <sbdegu...@gmail.com
>>>>>>> > wrote:
>>>>>>>
>>>>>>>> There are two patterns I find in my code that I'm still unhappy
>>>>>>>> with but I don't know how to clean up.
>>>>>>>>
>>>>>>>> The first is: (if (:attr obj) obj (assoc obj :attr something))
>>>>>>>>
>>>>>>>> I'm basically saying, give this hash-map an attribute if it
>>>>>>>> doesn't already have it. And just return the thing with an attribute,
>>>>>>>> regardless if I had to add it or not.
>>>>>>>>
>>>>>>>> This version is ugly because it repeats obj three times. I could
>>>>>>>> write my own macro to de-duplicate it, but I avoid doing that when I
>>>>>>>> can
>>>>>>>> because there's usually a better built-in solution that I just don't
>>>>>>>> know
>>>>>>>> about yet.
>>>>>>>>
>>>>>>>> The second is like it: (if (some-test obj) obj
>>>>>>>> (some-transformation obj))
>>>>>>>>
>>>>>>>> In this one, I just want to return the object, but maybe
>>>>>>>> transform it first. But the reference to obj happens three times! Still
>>>>>>>> feels like it could be cleaned up.
>>>>>>>>
>>>>>>>> Any thoughts on how to clean these up?
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