On Wednesday, August 8, 2012 6:48:23 PM UTC+2, Brian Marick wrote:
>
> ... show the mechanics, but I'm looking for examples that would resonate
> more with an object-oriented programmer. Such examples might be ones that
> close over a number of values (which looks more like an object), or
> generate multiple functions that all close over a shared value (which looks
> more like an object), or use closures to avoid the need to have some
> particular argument passed from function to function (which looks like the
> `this` in an instance method).
>
You can make objects with its state hidden in a closure. E.g. if we want to
make a stack where people cannot look at any other element than the first
one, we can do that like this:
(letfn [(stack-fns [stack]
{:push (fn [elt] (stack-fns (conj stack elt)))
:pop (fn [] (stack-fns (pop stack)))
:peek (fn [] (peek stack))
:empty? (fn [] (empty? stack))})]
(defn new-stack []
(stack-fns [])))
Usage would be like this:
(let [stack (reduce
#((%1 :push) %2)
(new-stack)
(range 1 10))] ; To fill it with data
(loop [stack stack]
(if ((stack :empty?))
nil
(let [h ((stack :peek))
t ((stack :pop))]
(prn h)
(recur t)))))
And this will print the numbers 9 to 1, before returning nil.
The Joy of Clojure looks at this from p. 138 to 141, so I take no credit
for the idea - give that to the authors.
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
