* Rasmus Villemoes <li...@rasmusvillemoes.dk> wrote:
> +#define _COMMA ,
> +#define _COND_PUNCTUATION_0(p)
> +#define _COND_PUNCTUATION_1(p) p
> +
> +#define CHOOSE_EXPR(cfg, expr, ...) _CHOOSE_EXPR(cfg, expr, ##__VA_ARGS__,
> /* empty defalt arg */)
> +#define _CHOOSE_EXPR(cfg, expr, def, ...)
> __CHOOSE_EXPR(__ARG_PLACEHOLDER_##cfg, expr, def)
> +#define __CHOOSE_EXPR(arg1_or_junk, expr, def) ___CHOOSE_EXPR(arg1_or_junk
> expr, def)
> +#define ___CHOOSE_EXPR(__ignored, expr, ...) expr
> +
> +#define COND_DECLARATION(cfg, decl) _COND_DECLARATION(cfg, decl,
> CHOOSE_EXPR(cfg, 1, 0))
> +#define _COND_DECLARATION(cfg, decl, sfx) __COND_DECLARATION(cfg, decl, sfx)
> +#define __COND_DECLARATION(cfg, decl, sfx) CHOOSE_EXPR(cfg, decl)
> _COND_PUNCTUATION_##sfx(;)
> +#define COND_INITIALIZER(cfg, init) _COND_INITIALIZER(cfg, init,
> CHOOSE_EXPR(cfg, 1, 0))
> +#define _COND_INITIALIZER(cfg, init, sfx) __COND_INITIALIZER(cfg, init, sfx)
> +#define __COND_INITIALIZER(cfg, init, sfx) CHOOSE_EXPR(cfg, init)
> _COND_PUNCTUATION_##sfx(_COMMA)
Pet peeve, mind structuring this in a typographically more readable fashion, by
adding some common-sense vertical structure to the definitions:
#define CHOOSE_EXPR(cfg, expr, ...) _CHOOSE_EXPR(cfg, expr,
##__VA_ARGS__, /* empty defalt arg */)
#define _CHOOSE_EXPR(cfg, expr, def, ...)
__CHOOSE_EXPR(__ARG_PLACEHOLDER_##cfg, expr, def)
#define __CHOOSE_EXPR(arg1_or_junk, expr, def) ___CHOOSE_EXPR(arg1_or_junk
expr, def)
#define ___CHOOSE_EXPR(__ignored, expr, ...) expr
#define COND_DECLARATION(cfg, decl) _COND_DECLARATION(cfg, decl,
CHOOSE_EXPR(cfg, 1, 0))
#define _COND_DECLARATION(cfg, decl, sfx) __COND_DECLARATION(cfg, decl, sfx)
#define __COND_DECLARATION(cfg, decl, sfx) CHOOSE_EXPR(cfg, decl)
_COND_PUNCTUATION_##sfx(;)
#define COND_INITIALIZER(cfg, init) _COND_INITIALIZER(cfg, init,
CHOOSE_EXPR(cfg, 1, 0))
#define _COND_INITIALIZER(cfg, init, sfx) __COND_INITIALIZER(cfg, init, sfx)
#define __COND_INITIALIZER(cfg, init, sfx) CHOOSE_EXPR(cfg, init)
_COND_PUNCTUATION_##sfx(_COMMA)
?
It's still a mouthful, but at least readable at a glance.
Thanks,
Ingo
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