Walter Bright wrote:
> New const/invariant/enum in 2.009!
> 
> http://www.digitalmars.com/d/1.0/changelog.html http://ftp.digitalmars.com/dmd.1.025.zip
> 
> http://www.digitalmars.com/d/changelog.html http://ftp.digitalmars.com/dmd.2.009.zip

Finally, I can try to break it. It was no fun too break something that
was already thrown out (
http://www.digitalmars.com/d/archives/digitalmars/D/Invariants_broken_with_out_cast_63199.html
).

On Tue, 01 Jan 2008 12:37:38 +0300, Walter Bright <newshound1@digitalmars.com> wrote:

> New const/invariant/enum in 2.009!

I have tried this sample:

import std.stdio;

class Notifier
  {
    int i;

    this( int i_value )
      {
        i = i_value;
      }
  }

class Message
  {
    public Notifier notifier;

    this( Notifier notifier_object )
      {
        notifier = notifier_object;
      }
  }

void
main()
  {
    void show( Message m )
      {
        writefln( &m.notifier, ": ", m.notifier.i );
      }

    auto m1 = new Message( new Notifier( 1 ) );
    show( m1 );

    auto m2 = new invariant(Message)( new Notifier( 2 ) );
    show( m2 );
    m2.notifier = new Notifier( 3 );
    show( m2 );
  }

and got:

882FF8: 1
882FD8: 2
882FD8: 3

Why m2 is not an invariant object?

-- 
Regards,
Yauheni Akhotnikau

eao197 wrote:
I've modified 3 lines in your main function:

> void
> main()
>    {
>      void show( Message m )
       void show( in Message m )

>        {
>          writefln( &m.notifier, ": ", m.notifier.i );
           writefln( cast(Notifier*)&m.notifier, ": ", m.notifier.i );

>        }
> 
>      auto m1 = new Message( new Notifier( 1 ) );
>      show( m1 );
> 
>      auto m2 = new invariant(Message)( new Notifier( 2 ) );
       auto m2 = cast(invariant) new Message( new Notifier( 2 ) );

>      show( m2 );
>      m2.notifier = new Notifier( 3 );
>      show( m2 );
>    }
> 

With these changes, I get the error "Error: cannot modify const/invariant m2.notifier".

On Sat, 12 Jan 2008 23:26:58 +0300, torhu <no@spam.invalid> wrote:

> eao197 wrote:
> I've modified 3 lines in your main function:
>
>> void
>> main()
>>    {
>>      void show( Message m )
>         void show( in Message m )
>
>>        {
>>          writefln( &m.notifier, ": ", m.notifier.i );
>             writefln( cast(Notifier*)&m.notifier, ": ", m.notifier.i );
>
>>        }
>>       auto m1 = new Message( new Notifier( 1 ) );
>>      show( m1 );
>>       auto m2 = new invariant(Message)( new Notifier( 2 ) );
>         auto m2 = cast(invariant) new Message( new Notifier( 2 ) );
>
>>      show( m2 );
>>      m2.notifier = new Notifier( 3 );
>>      show( m2 );
>>    }
>>
>
> With these changes, I get the error "Error: cannot modify const/invariant m2.notifier".

But what 'new invariant(Message)' is supposed to do? I can't find it in the docs.

naryl wrote:
> But what 'new invariant(Message)' is supposed to do? I can't find it in  the docs.

As far as I know, it doesn't do anything.  DMD allows some syntaxes that have no effect.  It's a bit confusing sometimes.

eao197 wrote:
> Why m2 is not an invariant object?

It is, and it's a compiler bug that will get fixed.