Thanks, a lot!
It seems that there is no nice way to make a shortened lambda function
which returns an integer.
I mean #(1) is not OK, and #1 is not OK. Although there is no problem
with this (fn [] 1).
On Apr 18, 5:48 pm, "Stephen C. Gilardi" <squee...@mac.com> wrote:
> On Apr 18, 2010, at 9:21 AM, Yonov wrote:
>
>
>
> > Hi,
> > I am trying to implement memoize myself and have stucked on one place
> > for a lot of time. This is the code:
>
> > (defn mymemoize [func]
> > (let [dict (ref (hash-map))
> > inner #((let
> > [val (@dict %)]
> > (if (nil? val)
> > (do (dosync (alter dict conj {% (func %)})) (println (class
> > (@dict %))) (@dict %))
> > val)))]
> > inner))
>
> > (defn gg [x]
> > (if (= x 1) 1 2))
> > (def ff (mymemoize gg))
> > (ff 1)
>
> > I am printing only for debuging purposes. Actually everything in the
> > do-block is OK, but there is no return value. Why?
>
> The body of your anonymous function literal (#()) has an extra level of
> parentheses. Your code is coming up with the correct answer (the Integer 1)
> and then trying to execute it with no arguments. That's what this exception:
>
> java.lang.ClassCastException: java.lang.Integer cannot be cast to
> clojure.lang.IFn (NO_SOURCE_FILE:0)
>
> is trying to convey:
>
> This works:
>
> (defn mymemoize [func]
> (let [dict (ref (hash-map))
> inner #(let [val (@dict %)]
> (if (nil? val)
> (do (dosync (alter dict conj {% (func %)}))
> (println (class (@dict %)))
> (@dict %))
> val))]
> inner))
>
> --Steve
>
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