Re: immutable singleton pattern with static opCall

[Steven Schveighoffer]

On Mon, 28 Jun 2010 08:40:36 -0400, Justin Johansson <n...@spam.com> wrote:

Steven Schveighoffer wrote:

On Mon, 28 Jun 2010 08:07:40 -0400, Justin Johansson <n...@spam.com> wrote:

Steven Schveighoffer wrote:

To go one step further, if you want it to truly be a singleton type, you should mark the constructor private.

 -Steve

Indeed.  I forgot the private constructor in this version but had it
in earlier versions.

Continuing on with the saga, it's a pity that immutable
is not compatible with Object toString method without a cast.

class Foo
{
    static immutable private Foo instance;

    static this() {
       instance = new Foo;
    }

    static immutable(Foo) opCall() {
      return instance;
    }

immutable:
   private this() {}
}


void main()
{
    // numerous compile errors if the cast is left out
    stdout.writefln( "Foo() = %s", cast(Foo) Foo());
}

That's because toString should be a const function.

See http://d.puremagic.com/issues/show_bug.cgi?id=1824

please vote for the bug.

-Steve