Sorry, that one doesn't work. It worked in my repl, but I must have been
using old code.
On Wed, Aug 28, 2013 at 2:27 PM, Aaron Cohen <aa...@assonance.org> wrote:
> How about this alternative?
>
> (deftype Wrapper [f]
> clojure.lang.IFn
> (invoke [this] (f))
> (invoke [this a] (f a))
> ; repeat until you get bored
> )
>
> (defn e [f]
> (let [wr (Wrapper. f)]
> (eval `(~wr 1))))
>
> (e inc)
>
> (e (with-meta (fn [x] (+ 4 x)) {}))
>
>
>
> On Wed, Aug 28, 2013 at 1:59 PM, Jamie Brandon <
> ja...@scattered-thoughts.net> wrote:
>
>> That sort of works for my use case.
>>
>> What I want to do is define a grammar...
>>
>> (def num-graph
>> (graph
>> num ~(or ~succ ~zero)
>> succ (succ ^x ~num)
>> zero zero))
>>
>> ... attach actions ....
>>
>> (def num-out
>> (output-in num-graph
>> 'zero (fnk [] 0)
>> 'succ (fnk [x] (inc x))))
>>
>> ... and compile the result ...
>>
>> strucjure.regression.tests> (graph->view 'num num-out)
>> (clojure.core/letfn
>> [(num ...)
>> (succ ...)
>> (zero ...)]
>> (clojure.core/fn
>> [input__2288__auto__]
>> (num input__2288__auto__)))
>>
>> This works fine as long as the fnks dont close over anything, but
>> that's very limiting.
>>
>> If I eval that code and *then* wrap it in (binding ...) I can have
>> closures but that now means that I can't do call-site compilation.
>> I'll have to poke around a bit more...
>>
>> On 28 August 2013 18:32, Aaron Cohen <aa...@assonance.org> wrote:
>> > I'm not sure if you'll consider this hacky or not.
>> >
>> > (def ^:dynamic *fn-helper*)
>> >
>> > (defn eval-at-one [f] (binding [*fn-helper* f] (eval '(*fn-helper* 1))))
>> >
>> >
>> > On Wed, Aug 28, 2013 at 1:28 PM, Jamie Brandon
>> > <ja...@scattered-thoughts.net> wrote:
>> >>
>> >> You will also run into problems if your functions close over any data:
>> >>
>> >> user> (let [f (fn [] 1)] (eval `(~f)))
>> >> 1
>> >> nil
>> >> user> (let [x 1 f (fn [] x)] (eval `(~f)))
>> >> IllegalArgumentException No matching ctor found for class
>> >> user$eval38616$f__38617 clojure.lang.Reflector.invokeConstructor
>> >> (Reflector.java:163)
>> >>
>> >> I'm struggling with this as well, I'm definitely interested in finding
>> >> a non-hacky way to pass closures through eval without leaking memory.
>> >>
>> >> Perhaps something like:
>> >>
>> >> (let [x 1
>> >> f (fn [] x)
>> >> f-sym (gensym)]
>> >> (intern *ns* gensym (weak-ref f))
>> >> (with-meta (eval `(fn [] (do-stuff-with @~f))) {::strong-ref f}))
>> >>
>> >> So that way f will be freed up when the resulting fn is gced.
>> >>
>> >> On 28 August 2013 17:59, Ben Wolfson <wolf...@gmail.com> wrote:
>> >> > On Wed, Aug 28, 2013 at 9:27 AM, Jamie Brandon
>> >> > <ja...@scattered-thoughts.net> wrote:
>> >> >>
>> >> >>
>> >> >> If you aren't worried about leaking memory, a possible workaround is
>> >> >> to intern the fn in some namespace and then put the symbol in the
>> >> >> macro output.
>> >> >
>> >> >
>> >> > Hrm, I hope it doesn't come to that---as long as I'm creating the
>> >> > functions
>> >> > with their metadata, I can make things work, because I can add extra
>> >> > information to the with-meta call or do extra things when making the
>> >> > call.
>> >> > What I'd like, though, is for it to be possible to copy the metadata
>> >> > over to
>> >> > a new function by client code, just using the regular (with-meta (fn
>> >> > [blah]
>> >> > blah) (meta old-fn)) mechanism. But then the sneaky symbol, or
>> whatever
>> >> > extra thing, in the metadata, that's used in the form to be eval-ed
>> is
>> >> > pointing to the original function, not the one passed in. Maybe just
>> >> > providing a utility for fixing up the metadata is the right move,
>> though
>> >> > it's kidn of dissatisfying.
>> >> >
>> >> >
>> >> > --
>> >> > Ben Wolfson
>> >> > "Human kind has used its intelligence to vary the flavour of drinks,
>> >> > which
>> >> > may be sweet, aromatic, fermented or spirit-based. ... Family and
>> social
>> >> > life also offer numerous other occasions to consume drinks for
>> >> > pleasure."
>> >> > [Larousse, "Drink" entry]
>> >> >
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