[Haskell-cafe] Re: OCaml list sees abysmalLanguage Shootoutresults

[Ben Rudiak-Gould]

On Fri, 8 Oct 2004, Marcin 'Qrczak' Kowalczyk wrote:

> If the representation of some lists was changed, it would complicate
> all code which works on lists. Or maybe only polymorphic code, but
> it's still much. I don't believe it would be practical.

That's true in OCaml but not in the STG-machine, where heap objects are
accessed through a method-call interface. Adding new representations is
easy because the caller doesn't know what the representation is anyway.
GHC already uses a special packed representation for static Strings, and I
see no reason why the garbage collector couldn't in principle compact
lists as it copied them. I don't even see any reason why there couldn't be
a packing-aware (++), or a listGetBuf :: [a] -> Int -> (Array Int a, [a])
which noticed when a list was packed and used memcpy() as appropriate.
None of these optimizations would complicate or slow down other code which
used lists, though they would complicate the run-time system of course.

-- Ben