digitalmars.D - enumerating member offsetofs via foreach over members-tuple

"Denis Koroskin" <2korden gmail.com> Nov 14 2008

"Denis Koroskin" <2korden gmail.com> Nov 14 2008

deadimp <deadimp gmail.com> Nov 18 2008

"Denis Koroskin" <2korden gmail.com> Nov 14 2008
bearophile <bearophileHUGS lycos.com> Nov 14 2008
"Steven Schveighoffer" <schveiguy yahoo.com> Nov 14 2008
Frits van Bommel <fvbommel REMwOVExCAPSs.nl> Nov 14 2008
"Denis Koroskin" <2korden gmail.com> Nov 14 2008
"Denis Koroskin" <2korden gmail.com> Nov 14 2008
"Denis Koroskin" <2korden gmail.com> Nov 19 2008

"Denis Koroskin" <2korden gmail.com> writes:

I'm doing some meta stuff and came across a few problems.

First of is described here:  
http://d.puremagic.com/issues/show_bug.cgi?id=2454

Second one is slightly different and this time I am less sure whether it  
is a bug.
The following code is indetended to print offsets of all its members:

struct Test
{
     short s;
     int i;
     float f;
     double d;

     void test()
     {
         writefln("expected output:");
         writefln( cast(char*)&s - cast(char*)this ); //  
writefln(s.offsetof);
         writefln( cast(char*)&i - cast(char*)this ); //  
writefln(i.offsetof);
         writefln( cast(char*)&f - cast(char*)this ); //  
writefln(f.offsetof);
         writefln( cast(char*)&d - cast(char*)this ); //  
writefln(d.offsetof);

         writefln("actual output:");
         foreach (m; this.tupleof) {
             // writefln(m.offsetof); // Error: no property 'offsetof' for  
type 'short'
             writefln( cast(char*)&m - cast(char*)this);
         }
     }
}

expected output:
0
4
8
16

actual output:
-52
-48
-44
-40

Am I doing something wrong?

Nov 14 2008

"Denis Koroskin" <2korden gmail.com> writes:

On Fri, 14 Nov 2008 23:55:08 +0300, Denis Koroskin <2korden gmail.com>  
wrote:

 I'm doing some meta stuff and came across a few problems.

 First of is described here:  
 http://d.puremagic.com/issues/show_bug.cgi?id=2454

 Second one is slightly different and this time I am less sure whether it  
 is a bug.
 The following code is indetended to print offsets of all its members:

 struct Test
 {
      short s;
      int i;
      float f;
      double d;

      void test()
      {
          writefln("expected output:");
          writefln( cast(char*)&s - cast(char*)this ); //  
 writefln(s.offsetof);
          writefln( cast(char*)&i - cast(char*)this ); //  
 writefln(i.offsetof);
          writefln( cast(char*)&f - cast(char*)this ); //  
 writefln(f.offsetof);
          writefln( cast(char*)&d - cast(char*)this ); //  
 writefln(d.offsetof);

          writefln("actual output:");
          foreach (m; this.tupleof) {
              // writefln(m.offsetof); // Error: no property 'offsetof'  
 for type 'short'
              writefln( cast(char*)&m - cast(char*)this);
          }
      }
 }

 expected output:
 0
 4
 8
 16

 actual output:
 -52
 -48
 -44
 -40

 Am I doing something wrong?


One more found, can anyone explain error message, please? Is it valid or  
not?

template Test()
{
     void test()
     {
         foreach (m; this.tupleof) {
             writefln(typeof(m).stringof); // test.d(8): function  
test.B.Test!().test cannot access frame of function test
         }
     }
}

struct A
{
     float i;
     mixin Test!();
}

struct B
{
     A a;
     mixin Test!();
}

Nov 14 2008

deadimp <deadimp gmail.com> writes:

Denis Koroskin Wrote:

 On Fri, 14 Nov 2008 23:55:08 +0300, Denis Koroskin <2korden gmail.com>  
 wrote:
 
 One more found, can anyone explain error message, please? Is it valid or  
 not?
 
 template Test()
 {
      void test()
      {
          foreach (m; this.tupleof) {
              writefln(typeof(m).stringof); // test.d(8): function  
 test.B.Test!().test cannot access frame of function test
          }
      }
 }
 
 struct A
 {
      float i;
      mixin Test!();
 }
 
 struct B
 {
      A a;
      mixin Test!();
 }


Which compiler are you using?
I tested this on codepad.org and it worked.

Nov 18 2008

"Denis Koroskin" <2korden gmail.com> writes:

On Fri, 14 Nov 2008 23:55:08 +0300, Denis Koroskin <2korden gmail.com>  
wrote:

 I'm doing some meta stuff and came across a few problems.

 First of is described here:  
 http://d.puremagic.com/issues/show_bug.cgi?id=2454

 Second one is slightly different and this time I am less sure whether it  
 is a bug.
 The following code is indetended to print offsets of all its members:

 struct Test
 {
      short s;
      int i;
      float f;
      double d;

      void test()
      {
          writefln("expected output:");
          writefln( cast(char*)&s - cast(char*)this ); //  
 writefln(s.offsetof);
          writefln( cast(char*)&i - cast(char*)this ); //  
 writefln(i.offsetof);
          writefln( cast(char*)&f - cast(char*)this ); //  
 writefln(f.offsetof);
          writefln( cast(char*)&d - cast(char*)this ); //  
 writefln(d.offsetof);

          writefln("actual output:");
          foreach (m; this.tupleof) {
              // writefln(m.offsetof); // Error: no property 'offsetof'  
 for type 'short'
              writefln( cast(char*)&m - cast(char*)this);
          }
      }
 }

 expected output:
 0
 4
 8
 16

 actual output:
 -52
 -48
 -44
 -40

 Am I doing something wrong?


The following works but ...

struct Test
{
     short s;
     int i;
     float f;
     double d;

     void test()
     {
         foreach (i,m; this.tupleof) {
             // writefln(m.offsetof);
             writefln(cast(char*)&mixin(this.tupleof[i].stringof) -  
cast(char*)this);
         }
     }
}

There is definitely a room for improvement.

Nov 14 2008

bearophile <bearophileHUGS lycos.com> writes:

Denis Koroskin:
 First of is described here:  
 http://d.puremagic.com/issues/show_bug.cgi?id=2454


Just a note, the result is correct if you replace this line:
writefln(typeof(m).stringof);
With:
writefln(typeid(typeof(m)));

Bye,
bearophile

Nov 14 2008

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

"Denis Koroskin" wrote
 I'm doing some meta stuff and came across a few problems.

 First of is described here: 
 http://d.puremagic.com/issues/show_bug.cgi?id=2454


Bug reports without actual errors listed in them (i.e. 'try this and see 
what happens') will probably be ignored.  It would do you good to show what 
the errors are.

 Second one is slightly different and this time I am less sure whether it 
 is a bug.
 The following code is indetended to print offsets of all its members:

 struct Test
 {
     short s;
     int i;
     float f;
     double d;

     void test()
     {
         writefln("expected output:");
         writefln( cast(char*)&s - cast(char*)this ); // 
 writefln(s.offsetof);
         writefln( cast(char*)&i - cast(char*)this ); // 
 writefln(i.offsetof);
         writefln( cast(char*)&f - cast(char*)this ); // 
 writefln(f.offsetof);
         writefln( cast(char*)&d - cast(char*)this ); // 
 writefln(d.offsetof);

         writefln("actual output:");
         foreach (m; this.tupleof) {
             // writefln(m.offsetof); // Error: no property 'offsetof' for 
 type 'short'
             writefln( cast(char*)&m - cast(char*)this);
         }
     }
 }

 expected output:
 0
 4
 8
 16

 actual output:
 -52
 -48
 -44
 -40

 Am I doing something wrong?


Yes, in the code:

foreach(m; this.tupleof)

m is a variable local to the for loop, not a reference to the actual tuple 
member.

I'm not sure foreach(ref m; this.tupleof) will work, I haven't done much 
with tuples.

But certainly if ref m does work, the

writefln( cast(char *)&m - cast(char *)this);

should be accurate.

But m.offsetof probably won't, since at that point, m is simply a ref local 
variable, not a member of the struct.

I think possibly the only way offsetof works is in the form 
aggregate.member.offsetof.  I could be totally wrong.

-Steve

Nov 14 2008

Frits van Bommel <fvbommel REMwOVExCAPSs.nl> writes:

Denis Koroskin wrote:
 Am I doing something wrong?


As was mentioned, 'm' is just a local variable once inside the loop. 
This works though:
-----
foreach (i, m; this.tupleof) {
     writefln(this.tupleof[i].offsetof);
}
-----

Nov 14 2008

"Denis Koroskin" <2korden gmail.com> writes:

15.11.08 в 00:30 Steven Schveighoffer в своём письме
писал(а):

 "Denis Koroskin" wrote
 I'm doing some meta stuff and came across a few problems.

 First of is described here:
 http://d.puremagic.com/issues/show_bug.cgi?id=2454


 Bug reports without actual errors listed in them (i.e. 'try this and see
 what happens') will probably be ignored.  It would do you good to show  
 what
 the errors are.

 Second one is slightly different and this time I am less sure whether it
 is a bug.
 The following code is indetended to print offsets of all its members:

 struct Test
 {
     short s;
     int i;
     float f;
     double d;

     void test()
     {
         writefln("expected output:");
         writefln( cast(char*)&s - cast(char*)this ); //
 writefln(s.offsetof);
         writefln( cast(char*)&i - cast(char*)this ); //
 writefln(i.offsetof);
         writefln( cast(char*)&f - cast(char*)this ); //
 writefln(f.offsetof);
         writefln( cast(char*)&d - cast(char*)this ); //
 writefln(d.offsetof);

         writefln("actual output:");
         foreach (m; this.tupleof) {
             // writefln(m.offsetof); // Error: no property 'offsetof'  
 for
 type 'short'
             writefln( cast(char*)&m - cast(char*)this);
         }
     }
 }

 expected output:
 0
 4
 8
 16

 actual output:
 -52
 -48
 -44
 -40

 Am I doing something wrong?


 Yes, in the code:

 foreach(m; this.tupleof)

 m is a variable local to the for loop, not a reference to the actual  
 tuple
 member.

 I'm not sure foreach(ref m; this.tupleof) will work, I haven't done much
 with tuples.

 But certainly if ref m does work, the

 writefln( cast(char *)&m - cast(char *)this);

 should be accurate.

 But m.offsetof probably won't, since at that point, m is simply a ref  
 local
 variable, not a member of the struct.

 I think possibly the only way offsetof works is in the form
 aggregate.member.offsetof.  I could be totally wrong.

 -Steve


Ooops, sorry. I *hate* when others do like this but accidentially fell to  
the same trap. Thank you!

Nov 14 2008

"Denis Koroskin" <2korden gmail.com> writes:

15.11.08 в 01:47 Frits van Bommel в своём письме писал(а):

 Denis Koroskin wrote:
 Am I doing something wrong?


 As was mentioned, 'm' is just a local variable once inside the loop.  
 This works though:
 -----
 foreach (i, m; this.tupleof) {
      writefln(this.tupleof[i].offsetof);
 }
 -----


Ah, you are right. I knew I made a mistake somewhere! Thank you.

Nov 14 2008

"Denis Koroskin" <2korden gmail.com> writes:

On Wed, 19 Nov 2008 08:12:21 +0300, deadimp <deadimp gmail.com> wrote:

 Denis Koroskin Wrote:

 On Fri, 14 Nov 2008 23:55:08 +0300, Denis Koroskin <2korden gmail.com>
 wrote:

 One more found, can anyone explain error message, please? Is it valid or
 not?

 template Test()
 {
      void test()
      {
          foreach (m; this.tupleof) {
              writefln(typeof(m).stringof); // test.d(8): function
 test.B.Test!().test cannot access frame of function test
          }
      }
 }

 struct A
 {
      float i;
      mixin Test!();
 }

 struct B
 {
      A a;
      mixin Test!();
 }


 Which compiler are you using?
 I tested this on codepad.org and it worked.


Sorry, I forgot to mention - it's 2.020

Nov 19 2008

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digitalmars.D - enumerating member offsetofs via foreach over members-tuple