On Thu, Dec 15, 2011 at 8:56 PM, David Nolen <dnolen.li...@gmail.com> wrote:
> On Thu, Dec 15, 2011 at 8:16 PM, Cedric Greevey <cgree...@gmail.com> wrote:
>>
>> 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
>> }
>> }
>
>
> This is not a good idea. You then have to know the class of the fn to do the
> optimized dispatch. What's currently been done has left the door open for
> high performance higher order usage.
There is no possibility of "high performance higher order usage",
because primitives are boxed inside of collections. Unless you
proliferate int-vectors, double-vectors, long-seqs, and so forth and
map-longs, filter-doubles, remove-doubles, etc., etc., and that will
lead quickly to an unwieldy and messy API that will just leave
everyone longing for the way things used to be.
Meanwhile, what's currently been done makes for scarcely more
opportunities to reduce boxing than existed under 1.2.
Furthermore, even supposing someone adds, say, map-longs, there's
still a way to have the cake and eat it too. One could have all
*three* versions: MangledName implements IFn, if there're few enough
arguments one of the 1.3 interfaces, and has the static method. If one
of 1.3 interfaces is implemented, it can be used in the hypothetical
future map-longs. The four-argument limit then *only* applies to
*direct* higher-order use -- that is, (map-longs f s1 s2 s3 s4 s5)
would not work. If there were only four or fewer long-seqs, then f
would need to have four or fewer arguments and would then be capable
of having a 1.3 interface; or else f's position would be taken by a
closure that invoked the real f, something like #(f %1 42 %2 %4 0.5 %3
"mumble"), in which case the call to f is static rather than
higher-order (and can directly call the static optimized method of f's
class) and the closure can be compiled as a function with a 1.3
interface taking four longs.
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