On Monday, 10 December 2012 at 15:36:44 UTC, Joseph Rushton
Wakeling wrote:
On 12/09/2012 03:45 PM, Dan wrote:
Phobos can and should have a general dup function, capable of
duping (i.e.
recursive deep copy) structs without requiring any effort from
struct
developers. This can be done to cover the vast majority of
object copy issues
for structs
We already had some discussion about your gdup on d-learn, but
just for clarity -- it's possible to do a gidup as well as
gdup, correct?
I think so. Here is a claim I think is true: gdup must do full
deep copy to be safe and guarantee the transitive
const/immutable. If it is implemented such that there are no
casts, then the compiler does its job and ensures everything is
good. If there are casts they need to be deemed safe - I have one
cast to work around issues in associative array iteration.
Assuming that is fine - I claim that gidup or igdup or whatever
can just be:
@property auto gidup(T)(const ref T t) {
immutable(T) result = cast(immutable)(t.gdup);
return result;
}
auto another = c.gidup;
pragma(msg, typeof(another));
assertNotEquals(another.b.a.c.ptr, c.b.a.c.ptr);
assert(0==typesDeepCmp(another,c));
That is, since gdup does a full deep copy, casting the result to
immutable is fine as there is no aliasing.
Thanks,
Dan
