Question about version ( ) keyword

[Vincent R via Digitalmars-d]

Hi,

When looking at core definitions like core.sys.posix.pthread I 
can see some "duplicated" code because it seems version doesn't 
support Or as we would do in C/C++ with #ifdefined.
For instance if can read this:

version( CRuntime_Glibc )
{
     enum PTHREAD_BARRIER_SERIAL_THREAD = -1;

     int pthread_barrier_destroy(pthread_barrier_t*);
     int pthread_barrier_init(pthread_barrier_t*, in 
pthread_barrierattr_t*, uint);
     int pthread_barrier_wait(pthread_barrier_t*);
     int pthread_barrierattr_destroy(pthread_barrierattr_t*);
     int pthread_barrierattr_getpshared(in pthread_barrierattr_t*, 
int*);
     int pthread_barrierattr_init(pthread_barrierattr_t*);
     int pthread_barrierattr_setpshared(pthread_barrierattr_t*, 
int);
}
else version( FreeBSD )
{
     enum PTHREAD_BARRIER_SERIAL_THREAD = -1;

     int pthread_barrier_destroy(pthread_barrier_t*);
     int pthread_barrier_init(pthread_barrier_t*, in 
pthread_barrierattr_t*, uint);
     int pthread_barrier_wait(pthread_barrier_t*);
     int pthread_barrierattr_destroy(pthread_barrierattr_t*);
     int pthread_barrierattr_getpshared(in pthread_barrierattr_t*, 
int*);
     int pthread_barrierattr_init(pthread_barrierattr_t*);
     int pthread_barrierattr_setpshared(pthread_barrierattr_t*, 
int);
}
else version (OSX)
{
}
else version (Solaris)
{
     enum PTHREAD_BARRIER_SERIAL_THREAD = -2;

     int pthread_barrier_destroy(pthread_barrier_t*);
     int pthread_barrier_init(pthread_barrier_t*, in 
pthread_barrierattr_t*, uint);
     int pthread_barrier_wait(pthread_barrier_t*);
     int pthread_barrierattr_destroy(pthread_barrierattr_t*);
     int pthread_barrierattr_getpshared(in pthread_barrierattr_t*, 
int*);
     int pthread_barrierattr_init(pthread_barrierattr_t*);
     int pthread_barrierattr_setpshared(pthread_barrierattr_t*, 
int);
}
else version (CRuntime_Bionic)
{
}
else
{
     static assert(false, "Unsupported platform");
}

When I see this code I cannot help thinking of something like:

version( CRuntime_Glibc ) || version( FreeBSD ) || version 
(Solaris)
{
     if(version(Solaris))
	   enum PTHREAD_BARRIER_SERIAL_THREAD = -2;
	else
	   enum PTHREAD_BARRIER_SERIAL_THREAD = -1;
	
     int pthread_barrier_destroy(pthread_barrier_t*);
     int pthread_barrier_init(pthread_barrier_t*, in 
pthread_barrierattr_t*, uint);
     int pthread_barrier_wait(pthread_barrier_t*);
     int pthread_barrierattr_destroy(pthread_barrierattr_t*);
     int pthread_barrierattr_getpshared(in pthread_barrierattr_t*, 
int*);
     int pthread_barrierattr_init(pthread_barrierattr_t*);
     int pthread_barrierattr_setpshared(pthread_barrierattr_t*, 
int);
}
else version (OSX) ||version (CRuntime_Bionic)
{
}
else
{
     static assert(false, "Unsupported platform");
}

I suppose language creators had good reasons to not allow it but 
I am a bit disapointed by the aspect of this language because 
some files are really verbose.
However I understand that this limitation allow a clear 
separation between different platforms...