You can also pass functions (and closures) around in a map;
(defn my-app-uses-do-something
[map-with-cfg-stuff]
...
((:do-something map-with-cfg-stuff) 13 19)) )
(defn do-something-quickly [x y] ...
(defn do-something-elegantly [x y] ...
(my-app-uses-do-something
{:do-something do-something-quickly
:some-other-cfg-stuff [...whatever] } )
Another little example to drive home the point;
(defn uses-f [mp x y] ((:f mp) x y))
(defn f [x y] (+ x y))
(uses-f {:f f} 3 4)
7
uses-f {:f -} 3 4)
-1
(uses-f {:f #(+ (* %1 %2) 3)} 3 4)
15
It's really worthwhile getting one's head around higher order
functions and closures. It allows you to totally think out of the
(imperative) box. Don't pass the data to a function - pass the
function to some data!
Rgds, Adrian.
On Thu, Jul 16, 2009 at 10:33 PM, John Harrop<jharrop...@gmail.com> wrote:
> On Thu, Jul 16, 2009 at 11:34 AM, Dragan <draga...@gmail.com> wrote:
>>
>> Thanks for the tip, I meant something else.
>> Let's say that I want to write a function do-something. There could be
>> 2 implementations: do-something-quickly and do-something-elegantly.
>> The parameters are the same and there are no differences in their
>> "interface". I would like to be able to call it by writing (do-
>> something arg) in my code and specify which implementation I want to
>> use somewhere else (in the configuration part of the code).
>
> Functions are values you can pass around, so:
> (defn do-something-quickly [x y] ... )
> (defn do-something-elegantly [x y] ... )
> (defn do-various-things [do-something x y z w]
> (let [z (do-something x y)]
> ... ))
> user=> (do-various-things do-something-quickly 13 19 3 23)
> some-sort-of-output
> user=> (do-various-things do-something-elegantly 13 19 3 23)
> some-sort-of-output
>
> >
>
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