On Thursday, 29 March 2018 at 15:16:07 UTC, Ivan Kazmenko wrote:
So, why do delegates of guns[] and huns[] all return 1, and how
to correctly reproduce the behavior of funs[] while populating
it in a loop?
A delegate is a function with a pointer to the stack frame where
it was created. It doesn't copy or insert the value of 'i', it
still refers to the very same location in memory as the i from
the for-loop. After the for-loop, that value is 1, so all
delegates refering to that i return 1. The solution is to
generate a new local variable for each closure with a helper
function:
```
import std.stdio: writeln;
void main () {
int delegate () [] funs;
foreach(i; 0..2) {
funs ~= constantDelegate(i);
}
writeln(funs[0]()); //prints 0
writeln(funs[1]()); //prints 1
}
auto constantDelegate(int num) {
return () => num;
}
```
Note that since the delegate leaves the scope of
constantDelegate, the stack frame with the value for 'num' will
be allocated to the heap because local variables normally don't
persist after returning from a function.
