On 08/17/2016 08:38 PM, Engine Machine wrote:
On Wednesday, 17 August 2016 at 08:37:32 UTC, Lodovico Giaretta wrote:
[...]
You mean something like:
struct MySequence(Args...)
{
enum length = Args.length;
alias args = Args;
}
alias x = MySequence!(a, b, MySequence!(c, d));
static assert(x.length == 3)
static assert(x.args[2].length == 2);
Thanks, basically works.
How can I test, though, if a argument uses a MySequence? I can't do if
(Args[0] == MySequence) because MySequence is templated. While I could
test for a length, that doesn't work because some types have a length. I
could add another enum to MySequence, but again, not safe.
I could do some string tests, but that doesn't work.
in your exmaple,
if (x.args[2] == MySequence) ??
I simply need to differentiate between a parameter/arg being a
MySequence and not.
With MySequence being a type, you can do this:
----
static if (is(x.args[2] == MySequence!Args, Args ...))
{
...
}
----
Aside from this check, there is probably not much use for MySequence
being a type. So I'm be tempted to find a way to do the check with a raw
template MySequence.
As you said, another enum alone doesn't cut it. The faker can just add
the same enum.
But a private enum of a private type might do it:
----
template MySequence(Args ...)
{
/* ... length and args ... */
private enum id = Id();
}
private struct Id {}
enum isMySequence(alias seq) = is(typeof(seq.id) == Id);
----
Other modules can't use the Id type directly, because it's private. And
they can't use typeof(MySequence!foo.id), because the id member is
private, too.
However, I wouldn't be surprised if this can be circumvented too.
