Yup, something like that is gonna work.
Thanks!
On Tuesday, September 4, 2012 2:34:27 PM UTC-7, Mark Hamstra wrote:
>
> So I'm working on developing a Clojure api for a distributed data analysis
> framework. A key part of that has to be the ability to pass functions as
> parameters into various map, reduce, filter, groupBy, etc. functions.
> Since this a framework developed in Scala, these function parameters
> eventually become Scala Function1 or Function2. What I really want is to
> be able to use this framework interactively from the Clojure repl, much as
> it can already be done from the Scala repl. For example, it is possible in
> the Scala repl to do something like:
>
> aDataSet.map(n => n + 1)
>
> which, of course, increments every element in the data set by 1. What I
> am eventually working toward is being able to do the equivalent to the
> above Scala interaction in Clojure:
>
> user=> (framework-map #(+ % 1) aDataSet)
>
> but as an intermediate step, I'm trying to get named function-like
> parameters working before tackling anonymous functions. So, I'd be happy
> right now with:
>
> user=> (def f (...))
> #'user/f
> user=> (framework-map f aDataSet)
>
> I can actually get this to work if I use the Java api to the framework and
> use gen-class to AOT compile a class and then create an instance equivalent
> to:
>
> FrameworkFunction<Integer, Integer> f = new FrameworkFunction<Integer,
> Integer>()
> {public Integer call(Integer n) {return (n + 1)}}
>
> But needing to jump through all of the AOT hoops every time the user needs
> to pass a function as a parameter would put a major hitch in the
> interactive giddyup, so this isn't really an acceptable solution (although
> it does appear to work fine to statically create batch jobs for the
> framework, or to create a library of pre-defined functions that can passed
> in from the repl.) I haven't really tried to use the underlying Scala api
> directly from the Clojure repl, so if someone sees a way to make that work,
> then I'll gladly use less wrapper layers. Using the Java api from the
> Clojure repl mostly works, but my major hangup is with not being able to
> get a useful instance of the abstract FrameworkFunction class (and similar
> classes.) I can use proxy to create an instance that works equivalently
> directly within the repl to an instance of an AOT class, so I can do:
>
> user=> (.call f 2)
> 3
>
> regardless of whether f is an instance of a concrete AOT class extending
> FrameworkFunction or f is a proxy extending FrameworkFunction. But trying
> to pass the proxy as a parameter leads to trouble when the framework tries
> to do things with the .class file. For example, when the following chunk
> of Scala code is hit:
>
> private def getClassReader(cls: Class[_]): ClassReader = {
> logInfo("attempted class name: " + cls.getName.replaceFirst("^.*\\.",
> "") + ".class")
> new ClassReader(cls.getResourceAsStream(
> cls.getName.replaceFirst("^.*\\.", "") + ".class"))
> }
>
> the attempt to generate an ASM class reader from Function$0.class fails
> when using the proxy (IOException Class not found
> org.objectweb.asm.ClassReader.a (:-1)), but works fine using the AOT
> instance.
>
> So, the upshot of all of this is that I am wondering how I should go about
> creating in the repl instances of this FrameworkFunction abstract class
> that can be passed into the framework HOFs. Even better would be if
> someone could explain to me how in the repl to convert Clojure functions
> into Scala functions so that I could then pass them directly into the
> framework with less need for the Java wrapper.
>
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