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digitalmars.D.bugs - Anonymous unions

reply Derek Parnell <derek psych.ward> writes:
I think the code below is supposed to compile...

struct S
{
   union Anon
   {
      int Int;
      real Atom;
   }
}

void main()
{
    S test;

}

But I get this message ...

  test.d(13): need 'this' to access member Int


I need to change it to this to get it to compile ...

struct S
{
   union Anon
   {
      int Int;
      real Atom;
   }
   Anon A;
}

void main()
{
    S test;
    test.A.Int = 2;
}

-- 
Derek
Melbourne, Australia
1/06/2005 1:02:30 PM
May 31 2005
next sibling parent reply Hasan Aljudy <hasan.aljudy gmail.com> writes:
Derek Parnell wrote:

 I think the code below is supposed to compile...
 
 struct S
 {
    union Anon
    {
       int Int;
       real Atom;
    }
 }
 


I think anonymous unions have no names (hence anonymous)
So strictly speaking, the union above is probably not anonymous.

This should probably compile:
  struct S
  {
     union
     {
        int Int;
        real Atom;
     }
  }


 void main()
 {
     S test;

 }
 
 But I get this message ...
 
   test.d(13): need 'this' to access member Int


Anon is the type name, not an instance. I think that's why it needs a 
"this" (i.e. an instance)


 
 
 I need to change it to this to get it to compile ...
 
 struct S
 {
    union Anon
    {
       int Int;
       real Atom;
    }
    Anon A;
 }
 
 void main()
 {
     S test;
     test.A.Int = 2;
 }
 


This (I think) is c++'s way of doing it .. it's definitly not anonymous.
May 31 2005
parent reply Derek Parnell <derek psych.ward> writes:
On Tue, 31 May 2005 21:12:14 -0600, Hasan Aljudy wrote:


 Derek Parnell wrote:

 I think the code below is supposed to compile...
 
 struct S
 {
    union Anon
    {
       int Int;
       real Atom;
    }
 }
 


 
 I think anonymous unions have no names (hence anonymous)
 So strictly speaking, the union above is probably not anonymous.
 
 This should probably compile:
   struct S
   {
      union
      {
         int Int;
         real Atom;
      }
   }


Thanks. Yes it does. 

But I guess it means only one anonymous union per struct though ;-)

-- 
Derek
Melbourne, Australia
1/06/2005 1:26:13 PM
May 31 2005
parent reply Chris Sauls <ibisbasenji gmail.com> writes:
Derek Parnell wrote:

 But I guess it means only one anonymous union per struct though ;-)


Actually no, no it doesn't..  I just tested with this:
































Although granted, naming might be interesting when having multiple 
anonymous unions.

-- Chris Sauls
May 31 2005
parent Stewart Gordon <smjg_1998 yahoo.com> writes:
Chris Sauls wrote:
<snip>

 Although granted, naming might be interesting when having multiple 
 anonymous unions.


An anonymous union doesn't create a scope.  And so it's illegal for 
names to collide between them.

Stewart.

-- 
My e-mail is valid but not my primary mailbox.  Please keep replies on 
the 'group where everyone may benefit.
Jun 01 2005
prev sibling parent reply "Andrew Fedoniouk" <news terrainformatica.com> writes:
Derek, anonymous means 'no type name'
and not 'no variable name'

variable name - alias of some memory location
must always exist if you want to store something there.
So you should write something like this:

 struct S
  {
     union
     {
        int Int;
        real Atom;
     } var;
  }

And then

S s;
s.var.Int = 28;


Andrew.


"Derek Parnell" <derek psych.ward> wrote in message 
news:14ds0mvtn12la$.1nc9wu744dnbg.dlg 40tude.net...

I think the code below is supposed to compile...

 struct S
 {
   union Anon
   {
      int Int;
      real Atom;
   }
 }

 void main()
 {
    S test;

 }

 But I get this message ...

  test.d(13): need 'this' to access member Int


 I need to change it to this to get it to compile ...

 struct S
 {
   union Anon
   {
      int Int;
      real Atom;
   }
   Anon A;
 }

 void main()
 {
    S test;
    test.A.Int = 2;
 }

 -- 
 Derek
 Melbourne, Australia
 1/06/2005 1:02:30 PM
May 31 2005
parent reply Stewart Gordon <smjg_1998 yahoo.com> writes:
Andrew Fedoniouk wrote:

 Derek, anonymous means 'no type name'
 and not 'no variable name'
 
 variable name - alias of some memory location
 must always exist if you want to store something there.
 So you should write something like this:
 
  struct S
   {
      union
      {
         int Int;
         real Atom;
      } var;
   }


<snip top of upside-down reply>

Illegal in D.  Should be

     struct S
     {
         union Var
         {
             int Int;
             real Atom;
         }
         Var var;
     }

Stewart.

-- 
My e-mail is valid but not my primary mailbox.  Please keep replies on 
the 'group where everyone may benefit.
Jun 01 2005
parent "Andrew Fedoniouk" <news terrainformatica.com> writes:
"Stewart Gordon" <smjg_1998 yahoo.com> wrote in message 
news:d7klmr$2090$1 digitaldaemon.com...

 Andrew Fedoniouk wrote:

 Derek, anonymous means 'no type name'
 and not 'no variable name'

 variable name - alias of some memory location
 must always exist if you want to store something there.
 So you should write something like this:

  struct S
   {
      union
      {
         int Int;
         real Atom;
      } var;
   }


 <snip top of upside-down reply>

 Illegal in D.  Should be

     struct S
     {
         union Var
         {
             int Int;
             real Atom;
         }
         Var var;
     }

 Stewart.


Thanks Stewart. It was my Cism.
Jun 01 2005