Since the original question was in CLJS, which has neither `intern` nor
`eval`, does that mean the macro mapping another macro approach is the only
solution there?
On Thu, May 11, 2017 at 9:18 AM, Alan Thompson <clooj...@gmail.com> wrote:
> I like the idea of using `eval` and `memoize`. I'll have to keep that in
> mind.
> Alan
>
> On Thu, May 11, 2017 at 7:58 AM, Timothy Baldridge <tbaldri...@gmail.com>
> wrote:
>
>> This is a somewhat weird answer to a overcomplicated problem. As
>> mentioned, the data is a map to start with, and maps are functions so
>> treating the maps as data is probably the best approach. And like Dragan,
>> I'm unsure why this example doesn't use `(data :able)`.
>>
>> When I do need to generate functions at runtime, and I can't use macros
>> (for the reasons mentioned), I'll either use a macro that creates a var, or
>> use eval perhaps in conjunction with a memoize. I used this a lot in my
>> work with JavaFx. Do some reflection, generate some code, eval the code and
>> return a function, memoize that process so we can get the generated
>> function via name. So the interface looks like this:
>>
>> ((get-setter button :text) "hey")
>>
>> Get-setter does a ton of reflection, but calling the returned function
>> remains fast due to the combination of eval and memoization.
>>
>>
>>
>> On Thu, May 11, 2017 at 2:55 AM, Dragan Djuric <draga...@gmail.com>
>> wrote:
>>
>>> What's wrong with (foo :able) => "Adelicious!" and (:able foo) =>
>>> "Adelicious!"?
>>>
>>>
>>> On Thursday, May 11, 2017 at 9:20:19 AM UTC+2, Alan Thompson wrote:
>>>>
>>>> A recent question on StackOverflow raised the question of the best way
>>>> to automatically generate functions. Suppose you want to automate the
>>>> creation of code like this:
>>>>
>>>>
>>>>
>>>> (def foo
>>>> {:able "Adelicious!"
>>>> :baker "Barbrallicious!"
>>>> :charlie "Charlizable"})
>>>> (def bar
>>>> {:able "Apple"
>>>> :baker "Berry"
>>>> :charlie "Kumquat"})
>>>>
>>>> (defn manual-my-foo [item] (get foo item))
>>>> (defn manual-my-bar [item] (get bar item))
>>>>
>>>> (manual-my-foo :able) => "Adelicious!"
>>>> (manual-my-bar :charlie) => "Kumquat"
>>>>
>>>>
>>>> You could write a macro to generate one of these at a time, but you
>>>> can't pass a macro to a higher-order function like `map`, so while this
>>>> would work:
>>>>
>>>>
>>>> (generate-fn :foo) ;=> creates `my-foo` w/o hand-writing it
>>>>
>>>>
>>>> this wouldn't work:
>>>>
>>>>
>>>> (map generate-fn [:foo :bar :baz])
>>>>
>>>> While one could write a 2nd macro to replace `map`, this is a symptom
>>>> of the "Turtles All the Way Down" problem. One workaround is to avoid
>>>> macros altogether and use only functions to generate the required `my-foo`
>>>> and `my-bar` functions. The trick is to make use of the built-in Clojure
>>>> function `intern` both to save the newly generated functions into the
>>>> global environment and to retrieve the pre-existing maps `foo` and `bar`.
>>>> Full details are available Q&A-style at the StackOverflow post
>>>> <http://stackoverflow.com/questions/43904628/how-to-create-clojure-defn-functions-automatically/43904717#43904717>
>>>> .
>>>>
>>>> Enjoy,
>>>> Alan
>>>>
>>>> --
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>>
>>
>>
>> --
>> “One of the main causes of the fall of the Roman Empire was that–lacking
>> zero–they had no way to indicate successful termination of their C
>> programs.”
>> (Robert Firth)
>>
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>
>
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