[Ecls-list] Wrapping C++ constants...

[Dietrich Bollmann]

Hi Matt,

Thank you!

So the following works:

(let () (defconstant +xy-plane+ (ffi:c-inline () () :pointer-void "(void *)
&ON_xy_plane" :one-liner t)))

Here - just for reference - a link to the file contrib/sockets/sockets.lisp:


http://sourceforge.net/p/ecls/ecl/ci/master/tree/contrib/sockets/sockets.lisp

And another simple example with context:

Example:

  (ffi:clines "#define SOME_CONSTANT 123")
  (let () (defconstant +some-constant+ (ffi:c-inline () () :int
"SOME_CONSTANT" :one-liner t)))

Usage:

  (format t "+some-constant+: ~a~%" +some-constant+)

Output:

  +some-constant+: 123

I summarized your comments on the following page:
http://formgames.org/wiki/ECL/Wrapping_constants

Does it make sense to copy this / parts of it into the ECL Wiki?

All the best,

Dietrich




On Fri, Jul 12, 2013 at 12:35 AM, Matthew Mondor
<mm_lists at pulsar-zone.net>wrote:

> On Thu, 11 Jul 2013 20:26:11 +0900
> Dietrich Bollmann <dietrich at formgames.org> wrote:
>
> > I want to wrap a pointer to a C++ constant into a lisp constant.
> >
> > The following
> >
> >   (defconstant +xy-plane+
> >     (ffi:c-inline () () :pointer-void "(void *) &ON_xy_plane" :one-liner
> t))
> >
> > results in this error:
> [...]
> >
> > But this - at least to me - looks kind of unnecessarily cumbersome...
> >
> > Is there a better way to wrap a pointer to a constant from lisp?
>
> It's necessary to wrap those DEFCONSTANT inside a LET block so they are
> no longer top-level, see how contrib/sockets/sockets.lisp in the ECL
> source tree does it for instance.
> --
> Matt
>
>
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