On 1/20/11 12:47 PM, Jens Mueller wrote:
Andrei Alexandrescu wrote:
On 1/19/11 7:19 PM, Jens Mueller wrote:
Andrei Alexandrescu wrote:
Place the call to not!alwaysTrue in a local function inside main:
bool alwaysFalse(uint a) { return not!alwaysTrue(a); }
Thanks. Can you elaborate a bit please? I wonder why the alias won't
work.
I thought of it for a bit. It's a limitation of the compiler that's
worth a bug report. The explanation is a bit involved. Let me start
by remarking that if you prepend "static" to alwaysTrue, the alias
works as expected:
static bool alwaysTrue(uint a) { return true; }
alias not!(alwaysTrue) alwaysFalse;
Without "static", alwaysTrue has access to a hidden pointer to the
stack frame of the function is in.
Yeah. That makes sense.
It has this hidden pointer to access variables from the function it is
defined in.
In theory a template should be unable to manipulate alwaysTrue
because of that frame pointer. But Walter has had this great idea of
instantiating templates in the context of the function they're in,
so they gain access to the frame pointer too. However, that
instantiation mechanism still has a few limitations. I think the
code above runs into one of them.
I see.
I can file a bug report if it is considered important and should not be
forgotten.
Jens
Yes please. Make it an enhancement as it would remove a limitation of an
otherwise little explored feature. Thanks!
Andrei
