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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>
>
>
> --
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> zero–they had no way to indicate successful termination of their C
> programs.”
> (Robert Firth)
>
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