On Sunday, 29 March 2015 at 18:43:32 UTC, bitwise wrote:
I'm a little confused at this point why this doesn't work
either:
const(Test) test = new Test(); // fine
test = new Test(); // error
In C++, There is a clear distinction:
const Test *test1 = nullptr; // const before type
test1 = new Test(); // fine
Test *const test2 = nullptr; // const before identifier
test2 = new Test(); // error: test2 is readonly
Isn't there such a distinction in D?
Notice how you have that '*' there that allows you to distinguish
the data from the reference.
You can have a mutable pointer to const data in D, too:
struct Test {}
const(Test)* test1 = null;
test1 = new Test; /* fine */
const(Test*) test2 = null;
/* equivalent variant: const Test* test2 = null; */
test2 = new Test; /* Error: cannot modify const expression test2
*/
You cannot have a mutable class object reference to const data,
because syntactically that distinction isn't made in D. There is
std.typecons.Rebindable, though:
import std.typecons: Rebindable;
class Test {}
Rebindable!(const Test) test = null;
test = new Test; /* fine */
I would have suggested that I got things backward, but this
doesn't work either:
const Test test = new Test();
test = new Test(); // error: cannot modify const expression
`const Test test` is the same as `const(Test) test`.
