On 2/24/20 3:32 PM, H. S. Teoh wrote:
To fix this, copy the value of 'i' to a local variable inside the loop
body, then the lambda will correctly capture a unique per-iteration
instance of the variable. Like this:
foreach (i; iota(5))
{
auto _i = i;
printers[i] = () { write(_i); };
}
Nope. It doesn't ;) Because actually, _i is reused for the loop iteration.
You are thinking that the capture happens on the delegate creation. In
essence, it just sets a flag to the compiler that the enclosing function
must be placed on the heap.
Adam's method works because the nested call's stack frame is captured
when you return that delegate.
In other words, it looks like this:
void main()
{
static struct __mainStackFrame
{
int i;
int _i;
}
__mainStackFrame *frame = new __mainStackFrame; // here's where the
capture happens
with(*frame)
{
// main's function body, with all variables already being declared
}
}
-Steve
