On 7/30/17 12:19 AM, Matthew Gamble wrote:
I have a class member function from which I'm trying to return a sorted
array of key, value tuples stored in an associative array as a private
member. The member function should be able to be marked const to prevent
the AA from being modified. I have reduced the problem to the simple
case below which won't compile with DMD v2.072.2.
import std.array;
import std.algorithm;
class A
{
this() { aa = ["a":1, "b" : 2, "c" : 3]; }
auto pairs() @property const { return
aa.byPair.array.sort().release; }
private:
int[string] aa;
}
If I remove const from the pairs function it compiles fine. I'm just not
sure this is a behavior I want. Any help/recommendation would be
appreciated.
byPair must store a pointer to the data in the AA. If you mark the AA
const, then it must store a const pointer to AA data.
However, because we don't have tail modifiers, you can't construct just
one range that would make this work. We would need many different
ranges, one for each flavor of mutability.
So you are stuck doing what Ali recommended -- cast away the const.
In this case, no harm comes if you don't cast back to const (since the
value of the AA is `int`), but in general this solution isn't valid if
the value type contains references.
-Steve
