On Mon, Oct 29, 2007 at 12:35:20PM +0100, Joerg van den Hoff wrote:
> On Sun, Oct 28, 2007 at 08:07:46PM -0000, cultural_sublimation wrote:
> > Fellow Camels,
> >
> > How does one handle conditional compilation in OCaml? I want certain
> > pieces of debugging code to be included only if a certain environment
> > variable is set. This sort of thing is really easy to do in the C
> > preprocessor with #ifdefs.
> >
> > And yes, I know I can use cpp also with OCaml, but I was wondering
> > if there was a more "bactrian" way of doing this.
>
> is using `Sys.getenv' to simple minded and out of the
> question? this is not conditional compilation, sure, but if
> you use a reasonable "unprobable" name
> ("MYPROGRAM_DEBUGGING_OUTPUT" ...) for the environment
> variable, it would do the job, essentially.
Conditional code works for simple debugging case, but in other cases
you often need C-like macros, impotent as they may be compared to real
macros.
For example:
let package = "@PACKAGE@"
let version = "@VERSION@"
where @PACKAGE@ and @VERSION@ are substituted in your Makefile or
configure script. To do this, just isolate these definitions into a
separate module and use autoconf.
Another example:
let dialog =
#if LABLGTK <= 2.0
GDialog.dialog ~main_title:title ()
#else
GDialog.dialog ~title ()
#endif
[This isn't an exact example, but lablgtk does change the types of its
API calls often enough that compiling against several versions
requires C macros and cannot be done using ordinary if ... then ...
clauses].
Rich.
--
Richard Jones
Red Hat
