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

[David Leimbach]

On Fri, Oct 3, 2008 at 4:36 AM, minh thu <noteed at gmail.com> wrote:

> 2008/10/3 Mitchell, Neil <neil.mitchell.2 at credit-suisse.com>:
> >
> > 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.

Dave


>
> Thanks,
> Thu
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