I assume this is a real problem you are encountering since you wrote the
original Stack Overflow questions. As Dragan mentioned, this example
doesn't warrant such a complex solution, maps and keywords *are* function,
so all you really need is `foo` as a getter. Or even if they weren't
functions you still have `(partial get foo)`.
On Thu, May 11, 2017 at 10:27 AM, Alan Thompson <clooj...@gmail.com> wrote:
> 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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--
“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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