On 13.01.2011 2:16, Guilherme Vieira wrote:
No sh*t..?! @__@ That's so cool! But is it smart enough to know the
stack frame doesn't need to go to heap in this case? (since it returns
a heap object referecing another heap object, i.e. can it untangle `b'
from the stack?)
Ehm, it can optimize certain cases but for the moment it doesn't.
Still, it needs to store b somewhere, right? and delegate is 2 pointers
in fact, so b should go on heap anyway. So it narrows down to if it can
save only parts of the stack frame ...
--
Atenciosamente / Sincerely,
Guilherme ("n2liquid") Vieira
On Wed, Jan 12, 2011 at 11:49 AM, Dmitry Olshansky
<[email protected] <mailto:[email protected]>> wrote:
On 12.01.2011 16:07, Guilherme Vieira wrote:
Ah, I totally missed that. But what if `s' went out of the
scope and the scope ended? Wouldn't the scope reference (the
one containing `b') be lost and cause memory corruption?
E.g.:
Switch make_switch()
{
auto s = new Switch();
auto b = new ToggleButton();
s.watch = (Switch.State state) { b.toggled =
cast(bool)(state); };
return s;
}
That's the main point of built-in delegates - the compiler detects
them and places the enclosing stack frame on heap, so it's all
sort of cool magic that just works :)
--
Atenciosamente / Sincerely,
Guilherme ("n2liquid") Vieira
On Wed, Jan 12, 2011 at 10:57 AM, Dmitry Olshansky
<[email protected] <mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>>
wrote:
On 12.01.2011 15:41, Guilherme Vieira wrote:
Hi,
I'm wondering if a delegate adapter template like isn't
handy
for Phobos (it may be especially useful for std.signal):
class Switch
{
enum State { ON, OFF }
void trigger()
{
switch (mState)
{
case State.ON: mState = State..OFF; break;
case State.OFF: mState = State.ON; break;
default: break;
}
if (watch !is null) watch(mState);
}
void delegate(State s) watch;
private State mState;
}
class ToggleButton
{
@property toggled(bool toggled)
{
writeln("ToggleButton.toggled(", toggled, ")");
}
}
void main()
{
scope s = new Switch();
scope b = new ToggleButton();
s.watch = &b.toggled; // error: invalid conversion
s.watch = adapt!("obj.toggled = cast(bool)(a)",
Switch.State)(b);
s.trigger(); // prints `ToggleButton.toggled(true)`
s.trigger(); // prints `ToggleButton.toggled(false)`
s.trigger(); // prints `ToggleButton.toggled(true)`
s.trigger(); // prints `ToggleButton.toggled(false)`
}
Yes, it urges to be polished. Particularly, it doesn't
support
multiple arguments. I also wanted to place the argument
type
tuple somwhere else (actually wanted to hide it completely,
but I think that's not possible).
Feedback?
-- Atenciosamente / Sincerely,
Guilherme ("n2liquid") Vieira
How is it better then built-in language feature? This works
just fine:
void main()
{
//they can't be scope and compiler enforces this (+ scope is
deprecated)
//actually, the orignal code is unsafe - what hapens if adapted
delegate escapes current scope?
auto s = new Switch();
auto b = new ToggleButton();
s.watch = (Switch.State a){ b.toggled = cast(bool)a; };
s.trigger(); // prints `ToggleButton.toggled(true)`
s.trigger(); // prints `ToggleButton.toggled(false)`
s.trigger(); // prints `ToggleButton.toggled(true)`
s.trigger(); // prints `ToggleButton.toggled(false)`
}
-- Dmitry Olshansky
--
Dmitry Olshansky
--
Dmitry Olshansky
