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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