On Wednesday, 17 August 2016 at 19:15:48 UTC, ag0aep6g wrote:
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.
import std.traits: TemplateOf;
static if (__traits(isSame, TemplateOf!(x.args[2]), MySequence))
{
...
}
std.traits.TemplateOf extracts the symbol representing the
uninstantiated template.
__traits(isSame, symbol1, symbol2) evaluates at compile time to
true if and only if the two symbols represent the same thing (be
it a type, an uninstantiated template, an instantiated one or
whatever else).
