[cffi-devel] defenum proposal

[Justin Heyes-Jones]

On 1/24/06, efuzzyone at netscape.net <efuzzyone at netscape.net> wrote:
>
> Hello,
>    Another concern of the original post was how to handle anonymous C
> enums in cffi.
>
> Should one use `defconstants' for them? Or should cffi provide a
> mechanism to declare anonymous enums?
>
> As per my understanding cffi requires all enums to be named.
>
> Thanks.
> --
> Surendra Singhi
> http://ssinghi.kreeti.com/
>
>
> -----Original Message-----
> From: Luís Oliveira <luismbo at gmail.com>
> To: Frank Buss <fb at frank-buss.de>
> Cc: cffi-devel at common-lisp.net; justinhj at gmail.com; 'Surendra Singhi'
> <EFuzzyONE at netscape.net>
> Sent: Sun, 22 Jan 2006 15:56:45 +0000
> Subject: Re: [cffi-devel] defenum proposal
>
>   On 2006-jan-22, at 14:47, Frank Buss wrote:
>   > It is not necessary to use keywords like for the named enums,
> because
>   > unnamed enums in C are just syntatic sugar for a list of >
> "#define"s, which
>   > is mapped to a list of defconstants. I don't know, if this macro >
> fits in the
>   > philosophy of CFFI, perhaps in some utility class, and maybe with >
> another
> > name "defanonenum".
>
>   I don't really think of C's enum that way. If I want constants, I use
> #define (and defconstant in CL). If I want to represent some sort of
> entity or concept I use an enum (and symbols in CL). For example:
>
> #define MAX_COUNT 127
>
> (defconstant +max-count+ 127)
>
> vs.
>
> enum {
> RED,
> BLUE
> };
>
> :red, :blue (or 'red, 'blue)
>
> I suppose defcenum shouldn't force the user to use keywords though?
>
> --Luís Oliveira
> http://student.dei.uc.pt/~lmoliv/
> Equipa Portuguesa do Translation Project
> http://www.iro.umontreal.ca/translation/registry.cgi?team=pt
>
>
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The problem I am looking at is that SDL uses un-named enums quite a lot. In
addition it does arithmetic on them to create other enums...

enum
{
 a_value,
 another_value,
}

then it does

#define MAKE_MASK (n) (1<<n)

enum
{
  MAKE_MASK(a_value),
  MAKE_MASK(another_value)
}

In order to do this I can define a lisp function in my swig interface which
does the same thing, but for that to work you need someway of getting to the
value of the first enums.

Justin
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