Hi Soura. I think you have an extra set of parentheses in your second
example, on the line with dosync. It should read:
(defn foo2 [n]
(let [r (ref n)]
#(dosync
(alter r + %) @r)))
-- Scott
On Wed, Aug 26, 2009 at 2:40 PM, Sourav <soura.ja...@gmail.com> wrote:
>
> Hi,
>
> I'm new to clojure and came from a Lisp background. While learning I
> clojure I came accross the two different ways of creating anonymous
> functions ((fn ...) and #(...)). I tried to construct the accumulator
> function in clojure using these forms and this is what I wrote (this
> might seem naive but I'm just a beginner :)
>
> 1.
>
> (defn foo [n]
> (let [r (ref n)]
> (fn [i]
> (dosync
> (alter r + i) @r))))
> And it works fine:
>
> user> (def f (foo 10))
> #'user/f
> user> (f 1)
> 11
> user> (f 1)
> 12
>
> 2.
> (defn foo2 [n]
> (let [r (ref n)]
> #((dosync
> (alter r + %) @r))))
>
> This does not work:
> user> (def f (foo2 10))
> #'user/f
> user> (f 1)
> ; Evaluation aborted.
> java.lang.ClassCastException: java.lang.Integer cannot be cast to
> clojure.lang.IFn (NO_SOURCE_FILE:0)
> [Thrown class clojure.lang.Compiler$CompilerException]
>
> However, another different function defined below just works:
>
> user> (defn bar [n]
> #(+ n %))
> #'user/bar
> user> (def b (bar 10))
> #'user/b
> user> (b 1)
> 11
>
> Obviously I might be missing something... Please help.
>
> >
>
--
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