Guru, I'm not sure. Are you running it exactly the same way?
If you did...
(def y 1)
(def f (fn [x] (+ x y)))
...then I think that would result in two const fields instead, because
it stores the var #'y as a static field and calls getRawRoot on it at
runtime.
Otherwise I'm not sure.
On 26 November 2013 17:11, Guru Devanla <grd...@gmail.com> wrote:
> Hi Jamie,
>
> Thats interesting. How do I not let the compiler not optimize away the fact
> that y refers to the constant. When I run your program I have two constant
> fields defined rather than 'y. Am I missing something.
>
> Thanks
> Guru
>
>
> On Tue, Nov 26, 2013 at 6:16 AM, Jamie Brandon
> <ja...@scattered-thoughts.net> wrote:
>>
>> > (def f (let [y 1] (fn [x] (+ x y))))
>>
>> Let's have a look inside.
>>
>> > (require '[no.disassemble :refer [disassemble]])
>> > (println (disassemble f))
>> // Compiled from /home/jamie/strucjure/src/strucjure.clj (version 1.5
>> : 49.0, super bit)
>> public final class strucjure$fn__5589$fn__5590 extends
>> clojure.lang.AFunction {
>>
>> // Field descriptor #7 Lclojure/lang/Var;
>> public static final clojure.lang.Var const__0;
>>
>> // Field descriptor #25 Lclojure/lang/IPersistentMap;
>> final clojure.lang.IPersistentMap __meta;
>>
>> // Field descriptor #27 J
>> long y;
>> ....
>>
>> So there is the field you want.
>>
>> > (.y f)
>> java.lang.IllegalArgumentException: No matching field found: y for
>> class strucjure$eval5552$fn__5553 Reflector.java:271
>> clojure.lang.Reflector.getInstanceField Reflector.java:300
>> clojure.lang.Reflector.invokeNoArgInstanceMember
>> /home/jamie/strucjure/src/strucjure.clj:21 strucjure/eval5556
>>
>> Humbug.
>>
>> > (require '[clojure.reflect :refer [reflect]])
>> > (reflect f)
>> java.lang.ClassNotFoundException: strucjure$eval5552$fn__5553
>>
>> Interesting... I would love to know why that is the case.
>>
>> > (into [] (.. f getClass getDeclaredFields))
>>
>> [#<Field public static final clojure.lang.Var
>> strucjure$fn__5589$fn__5590.const__0> #<Field final
>> clojure.lang.IPersistentMap strucjure$fn__5589$fn__5590.__meta>
>> #<Field long strucjure$fn__5589$fn__5590.y>]
>>
>> > (defn get-field [instance field-name]
>> (let [field (first (filter #(= field-name (.getName %)) (.. instance
>> getClass getDeclaredFields)))]
>> (.setAccessible field true)
>> (.get field instance)))
>> > (get-field f "y")
>> 1
>>
>> Success! And just for fun:
>>
>> > (def f2 (strucjure$fn__5589$fn__5590 7))
>> > (f2 1)
>> 8
>>
>> I hope that helps. Now the more interesting question is why you would
>> want to do that...
>>
>>
>> On 21 November 2013 18:14, henry w <henryw...@gmail.com> wrote:
>> > Say you have a function created like this:
>> >
>> > (fn [x] (+ x y))
>> >
>> > and then you have a reference to an instance of this function, is there
>> > some
>> > way to use the function reference to access the list '(fn [x] (+ x y)),
>> > including the symbol 'y' (such that you could dereference 'y' and get
>> > its
>> > value)? The source function is not the right thing and so far googling
>> > hasn't got me the answer.
>> >
>> > Thanks
>> >
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