Re: passing flags to a function

[Dan McMahill]

Ludovic Courtès wrote:
> Hi,
>
> Dan McMahill <address@hidden> writes:
>
>
> > I can do something like
> >
> > SCM scm_myfn(SCM flags)
> > {
> >
> >  myfn (scm_num2int (flags, SCM_ARG1, "myfn"));
> >
> >  return SCM_BOOLEAN_T;
> >
> > }
> >
> > but I'm not sure of the best way to define the flags in scheme.  Or
> > maybe this is not "the scheme way".
>
>
> What you describe above is doable and is an approach sometimes taken.
> See for instance the POSIX functions in Guile, e.g., `popen'.
>
> Personally, I prefer to pass a list of symbols rather than a single
> number in such situations.  This might require some more work if you
> need to convert those flags to a C or'ed integer, but not so much
> because (i) symbols can be compared with `eq' which is fast, (ii)
> the list of flags may usually be small, and (iii) the number of values
> that can be taken by the flags is small as well.


Hi Ludovic,

Thanks for the reply. Could you show a short example of what the scheme 
function call might look like?

Are you meaning

(foo (list 'flag1 'flag2 'someotherflag))

I don't care much about speed in this particular case.

Thanks
-Dan