"Andrei Alexandrescu" <seewebsiteforem...@erdani.org> wrote in message
news:jk0naq$257e$1...@digitalmars.com...
>
> But why duplicate doItSlowWay(); which may be an arbitrarily long
> sequence?
If duplicating that block is a problem, there are other ways to do it.
version(ThisOS)
{
version = FastWayA;
}
else version(ThatOS)
{
version = FastWayB;
}
else version(SomeOS)
{
version = SlowWay;
}
else version(OtherOS)
{
version = SlowWay;
}
else
static assert(0, "OS not implemented");
version(FastWayA)
{
...
}
else version (FastWayB)
{
...
}
else version (SlowWay)
{
...
}
>
> This seems to accomplish little more than "well I didn't use else".
>
> Again: what exactly is wrong with specialization?
>
The advantage is, that when you write the code, you have _no idea_ what
platform/os it might need to run on in the future. You _cannot_ know which
version is most appropriate for _all_ new platforms, or even if any of them
will work at all. The only time to make this decision is when implementing
support for a specific platform, and this pattern forces you to consider
each place where platform specific behaviour is required. When doing things
like this, 100 false positives are much faster to fix than a single false
negative causing wrong code/corruption.
