• alxdef (29/29) Jun 22 2006 Hi there!
• Derek Parnell (109/139) Jun 22 2006 You have two choices.

alxdef <alxdef_member pathlink.com> writes:

Hi there!
I am beginner in D and I confused with subject.
Here my source:

Module some_mod.d ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
module some_mod;
struct struct1
{
union addr
{
struct
{
ushort offs;
ushort seg;
}
uint flat;
};
};
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In main.d ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
import some_mod;
struct1 s;
s.addr.flat = 0;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Compile command: DMD main.d some_mod.d

At this point compiler says the subject message. When I make 'offs', 'seg', and
'flat' as static compilation is well, but it is not what I need, cause fields of
union is unmodifiable. Could someone help with this?
Thanks a lot!

Sorry for my English!

Derek Parnell <derek nomail.afraid.org> writes:

On Fri, 23 Jun 2006 05:59:50 +0000 (UTC), alxdef wrote:

 Hi there!
 I am beginner in D and I confused with subject.
 Here my source:
 
 Module some_mod.d ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 module some_mod;
 struct struct1
 {
 union addr
 {
 struct
 {
 ushort offs;
 ushort seg;
 }
 uint flat;
 };
 };
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 In main.d ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 import some_mod;
 struct1 s;
 s.addr.flat = 0;
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Compile command: DMD main.d some_mod.d
 
 At this point compiler says the subject message. When I make 'offs', 'seg', and
 'flat' as static compilation is well, but it is not what I need, cause fields
of
 union is unmodifiable. Could someone help with this?
 Thanks a lot!

You have two choices.


 Module some_mod.d ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 module some_mod;
 struct struct1
 {
 union addr
 {
 struct
 {
 ushort offs;
 ushort seg;
 }
 uint flat;
 };
 addr a;
 };
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 In main.d ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 import some_mod;
 struct1 s;
 s.a.flat = 0;
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


 Module some_mod.d ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 module some_mod;
 struct struct1
 {
 union
 {
 struct
 {
 ushort offs;
 ushort seg;
 }
 uint flat;
 };
 };
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 In main.d ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 import some_mod;
 struct1 s;
 s.flat = 0;
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Now to explain...
The first choice uses a named Union. You called it 'addr'. But in D, can't
define a named union (or struct) and declare an instance of it in the same
statement. You have to use two statements ... for example:

   // Define the named union.
   union somename
   {
      int a;
      long b;
   }
   // Declare an instance of it.
   somename foo;

Once you have an instance of it, you can use it to access the union members
...

   foo.a = 1;

The second choice uses an unnamed (anonymous) union. In this case, when you
define a anonymous union you cannot declare an instance of separately
(because it doesn't have a name) so the definition also serves as the
declaration. You then access its members directly, again because there is
no instance name you can't use it.

   // Define the anonymous union.
   union 
   {
      int a;
      long b;
   }

Once you have an instance of it, you can use it to access the union members
...

   a = 1;

*But* you can only define anonymous unions and structs if there are inside
a union or struct. So the top-level container must have a name.


Anyhow, here your example reworked ...

---------some_mod.d -------------
module some_mod;
struct struct1
{
    union
    {
        struct
        {
            ushort offs;
            ushort segm;
        }
        uint flat;
    }
}
---------------------------------

----------- main.d ---------------
import some_mod;
import std.stdio;
void main()
{
    struct1 s;
    s.flat = 0xFFEEDDCC;
    writefln("%x %x", s.offs, s.segm);
}
---------------------------------

This displays "ddcc ffee" when run.

-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocrity!"
23/06/2006 4:21:25 PM