On 11/30/2010 09:30 AM, Jesse Phillips wrote:
This came up in discussion and I think the behavior is safe and usable when
wanting to change class data in a const function.
http://article.gmane.org/gmane.comp.lang.d.general/43476
One limitation is that value types declared as Mutable (Mutable!(int)) can not
be changed if the encapsulating class is declared immutable. For this reason a
Mutable value can not be changed inside a const function. I think this is
acceptable.
Another limitation appears to be an issue with alias this. It is commented as a
//FIXME in the code.
https://gist.github.com/721066
An example usage looks like:
class Inner { int n; }
class A {
Mutable!(int*) n;
Mutable!(int) n2;
Mutable!(Inner) innerClass;
this() { n = new int; innerClass = new Inner; }
void foo( int num ) {
n2 = num;
}
void bar( int num ) const {
innerClass.n = num;
}
}
auto aImmu = new immutable(A);
auto aMu = new A;
int i = 8;
*aImmu.n = i,
aImmu.bar(6),
*aMu.n = i,
aMu.n =&i,
aMu.n2 = i,
aMu.bar(6),
aMu.foo(6),
It is not enough to forward opAssign and opEquals. Any operator should
be handled. For example, change the implementation of A.foo to
n2 += 1;
and you will get a segfault during compilation.
You could add more kludge with operator overloads but I don't think it
is worth the effort. It makes more sense to wait until "alias this" bugs
are fixed. On the other hand, we may wait forever since the way "alias
this" should handle operators has never been specified.
