Re: Can someone explain why i can change this immutable variable please?

[Daniel Davidson]

On Wednesday, 9 October 2013 at 15:46:29 UTC, Gary Willoughby 
wrote:

So why does this give me an error i expect:
        import std.stdio;

        class Foo
        {
                public void change(string[] name)
                {
                        name[0] = "tess";
                        writeln(name);
                }
        }

        class Bar
        {
                private static immutable string name[] = ["gary"];

                public void test()
                {
                        auto foo = new Foo();
                        foo.change(this.name);
                }
        }

        void main(string[] args)
        {
                auto bar = new Bar();
                bar.test();
        }

Maybe this will help explain it:
void main() {
  pragma(msg, typeof(Bar.name));
  pragma(msg, typeof(Foo.change));
}
will print:

immutable(char[][])
void(string[] name)

The latter is really:

void(immutable(char)[] name)

The former is really:
immutable(immutable(immutable(char)[])[])

So for name the whole kit and kaboodle is immutable and you can 
not pass the whole immutable thing into something that is only 
immutable at one level.

Thanks
Dan