It's not "silly", it's the fastest way to dispatch fn calls...
> On Thu, Dec 15, 2011 at 8:05 PM, Softaddicts
> <lprefonta...@softaddicts.ca> wrote:
> > From a JVM perspective, f(& arglist) is a one arg function.
> > Try defining a fn with more than 20 args and you will get the
> > "can't specify more than 20 arguments...." error.
> > This is the maximum supported by the Clojure runtime for "non-optimized"
> > fns.
>
> Well, that's just silly, since a simple change to the fn macro would
> make that go away without any hassle, as I already outlined. (The
> error would remain for direct users of fn*, of course.)
>
> > One can argue about the argument size limit of optimized fn calls. Maybe 4
> > is too low.
> > These limitations has David pointed out are indirectly inherited from the
> > JVM architecture.
>
> As I understand it, the problem is a combinatorial explosion of
> interfaces with various signatures. Which is only a problem because,
> for some reason, static calls to optimized fns are not made directly
> to the fn's class. Why not just make an optimized fn class look like
>
> public class MangledName implements IFn {
> public Object invoke () { // unoptimized zero-arg version or arity
> throw goes here }
> public Object invoke (Object x) { // unoptimized one-arg version ... }
> ...
> public static long optimized (int bar, double quux, Object
> fiddlefaddle, long x, long y, long z) {
> // optimized version goes here
> }
> }
>
> and an optimized call site produce the same bytecode as
>
> MangledName.optimized(a, b, c, d, e, f);
>
> with possible unboxing of some of the arguments, and possible boxing
> of the return value, depending on the context. An unoptimized call
> site would use the IFn interface and behave exactly as now or under
> Clojure 1.2.
>
> > There are multiple ways to work around this limit. Destructuring, passing a
> > map, ...
>
> All of those box any primitives as part of wrapping them in collections.
>
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