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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