Re: [Haskell-cafe] Hmm, what license to use?

3 Oct 2008

      On Fri, 2008-10-03 at 10:08 -0700, David Leimbach wrote:
...
On Fri, Oct 3, 2008 at 4:36 AM, minh thu  wrote:
        2008/10/3 Mitchell, Neil :
>
        > Hi
        >
        >
        >> > > You mean shared libraries without the opportunity to
        >> inline library code?
        >> > > This would result in a huge performance loss, I think.
        >> >
        >> > Usually _mild_ performance loss, in exchange for major
        code-size
        >> > savings, I would think. C obviously has worked quite fine
        under
        >> > exactly this restraint (though C implementations
        obviously aren't
        >> > built to take as great advantage of inlining library code
        >> as Haskell may be).
        >>
        >> I think that the performance loss is much higher in the
        case
        >> of Haskell because of Lazy Evaluation, massive use of
        higher
        >> order functions and possibly more.
        >
        > Example 1:
        >
        > foo x | "test" `isPrefixOf` xs = ...
        >        | otherwise = ...
        >
        > If you have cross-module inlining, you get the rather
        obvious if like
        > construct. If you don't, you have to evaluate otherwise and
        test its
        > value.
        >
        > Example 2:
        >
        > (a :: Int) + b
        >
        > If you have cross-module specialisation you get a primitive
        integer
        > arithmetic instruction (possibly with a bit of unboxing,
        although often
        > not). If you don't, you get a dictionary lookup, followed by
        a higher
        > order application.
        >
        > One reason cross-module inlining is essential is that many
        Haskell
        > functions don't do very much, think of (+), (||), (>>), not,
        otherwise
        > etc. In C these would be built-in's, so are always available
        to the
        > optimiser (and usually just one instruction), in Haskell you
        need to get
        > them from the Prelude.
What happens in the C++ world where good chunk of
        functionnalities are
        in header files (templates or inline methods);
        is there the same LGPL problem that the one discussed here
        w.r.t.
        static/shared linking ?
I don't know what happens on platforms that don't have shared
libraries with LGPL.  If you build stuff statically, I'm pretty sure
you can't claim stuff is loosely coupled.
What I've always heard is that in that case you have to distribute
object files.

This would work for Haskell, except that changing the distributed
library is still liable to invalidate the object files, due to
cross-module inlining.

jcc

Re: [Haskell-cafe] Hmm, what license to use?

Jonathan Cast