On Sunday, 7 August 2016 at 20:48:29 UTC, ag0aep6g wrote:
On 08/07/2016 10:01 PM, Engine Machine wrote:
@nogc void foo(void delegate(int x) @nogc f);
fails with the @nogc.
Compiles just fine for me.
2nd, I cannot use a delegate because of the @nogc context,
Delegates don't necessarily need a GC allocation. They only
need it when they need a closure. Delegates of methods don't
need closures. And when you pass the delegate in a `scope`
parameter, no closure is needed, either.
Well, one can't pick the case the delegate is passed. When I use
a delegate in the nogc context it errs.
[...]
So, to get around these problems, I have to do something like
this:
alias callback(Args) = @nogc void function(int x, Args);
@nogc void foo(Args...)(callback!Args f, auto ref Args args,
int extra = 0)
The problem with this is that I can't seem to add f inline:
foo!string((int x, string s) { }, 1);
this fails with template mismatch.
You're missing an argument there. The second parameter of foo
is `args` which is `string` here. This call works:
foo!string((int x, string s) { }, "", 1);
Yeah, that was just a typeo obvious. That's not the reason it
fails.
But if I define the lambda outside it works:
auto f = (int x, string s) { };
foo!string(f, 1);
Doesn't work for me. Still missing the string argument.
Yes, same typo.
The problem with this is that when I want to pass no arguments,
auto f = (int x) { };
foo(f, 1);
fails. It seems that Args... requires at least one argument to
match the
template? This may be a bug?
One thing you need to fix: The `callback` template needs a
template sequence parameter (i.e. `Args...`). Otherwise it
takes exactly one type.
I did try that first and it didn't work. it works without ...,
and I figured that it is a template parameter and can also
represent a sequence? But I only tried with one argument so it
worked.
I added ... but same problems.
That doesn't make it work, though. You also need to add empty
template instantiation parentheses (i.e. `foo!()`), and you
need to remove `auto ref` from the `args` parameter.
No idea why it doesn't work with `auto ref`. At least that part
looks like a bug to me.
Yeah, so, this is typically what happens. One bug makes me change
my tail for two hours ;/
