Groveler and HUGE_VAL

[Zach]

Thanks Martin, that's just what I'll do.

However, isn't the entire point of a groveler to build a little C program
that gathers information like this for later use?  If one were to write a
general purpose way to do this, wouldn't the logical place to put that code
be in cffi-groveler?  Is the main hurdle here the fact that HUGE_VAL
doesn't necessarily have a representation as a Lisp interger or
double-float, the only two types that cvar allows?  Even though some of
these sound a bit rhetorical, these are honest questions.

Zach



On Fri, Apr 26, 2013 at 8:25 AM, Martin Simmons <martin at lispworks.com>wrote:

> >>>>> On Thu, 25 Apr 2013 20:55:38 -0600, Zach  said:
> >
> > > (constant (+huge-val+ "HUGE_VAL") :type integer)
> > >
> > > then
> > >
> > > (with-foreign-object (huge-ptr :uint64)
> > >    (setf (mem-ref huge-ptr :uint64) +huge-val+)
> > >   (nlopt-set-lower-bound opts huge-ptr))
> >
> > I have also been thinking along these lines.  The only thing I worry
> about
> > is whether this is strictly correct or just correct in practice.  Is
> there
> > a guarantee that a double float is always the same size as a uint64.
>  It's
> > true on every platform I have ever programmed for (I think), but will it
> > always be true?  Back when I programmed in C more often, hard coding data
> > type sizes into a program just seemed wrong so I didn't do it, so I
> guess I
> > wouldn't know.  Perhaps I am sweating a non-issue...
>
> That's not the only problem -- on some platforms, HUGE_VAL is not a
> compile-time constant.  It looks like the only portable way to get the
> value
> is to write a C helper function to return it.
>
> --
> Martin Simmons
> LispWorks Ltd
> http://www.lispworks.com/
>
>
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