On Fri, 14 Mar 2014 10:11:25 -0400, Ethan <goober...@gmail.com> wrote:
On Friday, 14 March 2014 at 14:02:06 UTC, Steven Schveighoffer
wrote:
And for that point, your demonstration has failed :)
It's an extraordinarily simple use case, but it is still quite a
common pattern in C++ defines, ie:
#ifdef _DEBUG
#define FEATUREA
#define FEATUREB
#define FEATUREC
#else
#define FEATUREB
#define FEATUREC
#endif
#ifdef FEATUREB
...
#endif
No, not really, there was no else in the version. It's when you have two
different versions that may trigger the same definition.
#if defined(MODEA) || defined(MODEB)
#define FEATUREA
#define FEATUREB
#endif
In D, this is:
version(MODEA) version = USEFEATUREAANDB;
version(MODEB) version = USEFEATUREAANDB;
...
version(USEFEATUREAANDB) // imagine reading this first, and wondering what
causes it to compile.
{
version = FEATUREA;
version = FEATUREB;
}
It's the equivalent of this in C:
#ifdef MODEA
#define USEFEATUREAANDB
#endif
#ifdef MODEB
#define USEFEATUREAANDB
#endif
...
#ifdef USEFEATUREAANDB
#define FEATUREA
#define FEATUREB
#endif
Yes, there are real world examples where the lack of logical or makes
things difficult to read. It's not all about versioning based on OS or
boolean flags.
-Steve
