On Thursday, 19 September 2013 at 16:47:13 UTC, Daniel Davidson
wrote:
Multi-part question:
1) Why does the last line fail? If cast to immutable how is it
different than z? I know it is related to the ref. I'm using
ref because I think it is likely more efficient - so assume the
char[16] were really char[1024].
2) If I got rid of the ref, how many copies of the data would
be made? And without looking at assembly what is a good way to
answer this question? I've tried to add this(this) to other
Stuff type structures to print when they are being called, but
that does not work because no logic can be in the default
constructor.
3) Also, is storing immutable(STUFF) in a struct in the general
case (as opposed to just this one) useful or silly?
Thanks
Dan
import std.stdio;
alias char[16] Stuff;
struct T
{
immutable(Stuff) myData;
this(ref immutable(Stuff) data) {
myData = data;
}
}
void main() {
immutable(Stuff) iData = "1234567890123456";
Stuff data = "1234567890123456";
writeln(T(iData));
auto iData2 = cast(immutable)data;
writeln(T(iData2));
// WHY DOES THIS FAIL WHEN T(iData2) works?
// writeln(T(cast(immutable)data));
}
cast(immutable)data) is not an lvalue, it's a rvalue. ref accepts
only lvalues.
