On Monday, 22 May 2017 at 13:52:35 UTC, Dukc wrote:
On Monday, 22 May 2017 at 13:11:15 UTC, Andrew Edwards wrote:
Sorry if this is a stupid question but it eludes me. In the
following, what is THING? What is SOME_THING?
[...]
I assume you know that the above part is c/c++ preprocessor,
which is not normally used at d?
Yes, I am aware.
THING is nothing there. If you use it at code, I'm not sure how
it behaves. Either it does not compile at all, or it behaves as
nothing (think whitespace). If it's the latter, SOME_THING
would be a lone asterix. Can be used as operator both unarily
and binarily. #IFNDEF regonizes all preprocessor declarations,
empty or not.
The closest D equivalent to #DEFINE is a string mixin. The
equivalent to above is:
static if (!is(typeof(thing))) enum thing = "";
static if (!is(typeof(someThing))) enum someThing = thing ~ "
*";
[...]
...you have to explicitly mix the text in:
@safe void main()
{ import std.stdio;
mixin("writeln(5 " ~ someThing ~ " 6);"); //30
}
That's really ugly... Hope I'll never have to resort to that. The
specific idiom does have it's uses though, as in the case of
self-important lookups.
[...]
-If the symbol is an empty declaration used only for #IFNDEFS,
version statements are a cood canditate for replacing it.
Perhaps that's what you're looking for?
Not exactly but I get the point. This list is golden, thanks for
the assist.
Andrew
