Is there a way to make a class variable visible but constant to outsiders, but changeable (mutable) to the class itself?

[dan via Digitalmars-d-learn]

Is it possible to have a class which has a variable which can be 
seen from the outside, but which can only be modified from the 
inside?

Something like:

class C {
   int my_var = 3;     // semi_const??
   void do_something() { my_var = 4; }
}

And then in another file

auto c = new C();
c.my_var = 5; // <<<- should trigger a compile-time error
writeln("the value is ", c.my_var);  // <<<- should print 3
c.do_something();
writeln("the value is ", c.my_var);  // <<<- should print 4

Reading Alexandrescu's book suggests the answer is "no" (the only 
relevant type qualifiers are private, package, protected, public, 
and export, and none seem appropriate).

(This effect could be simulated by making my_var into a function, 
but i don't want to do that.)

TIA for any info!

dan