Re: full path to source file __FILE__

[Jonathan M Davis via Digitalmars-d-learn]

On Friday, July 22, 2016 19:28:05 Jonathan Marler via Digitalmars-d-learn 
wrote:
> Actually I realized if __FILE__ was always absolute, then all
> your exception messages would contain the full path of the file
> it was thrown from on the machine it was compiled on. This would
> be quite odd.

In some cases, it could also be viewed as a security risk. For instance, on
*nix systems, it would almost certainly give away the username of the user
that built it.

Also, it would result in needlessly long error messages when exceptions were
thrown, which could impact performance as well as making log files that much
more annoying.

I'm definietly inclined to think that making __FILE__ absolute would be a
mistake. Maybe something else like __FILE_ABSOLUTE__ would be okay, but in
this particular case, I'd argue that you should just not make it a script if
you need additional files that are next to it rather than in a known place.
And as far as your example of build files goes, it's normal to have to run
stuff like that in the directory where it lives (e.g. that's what happens
with make), so while I understand that it may be annoying, I don't think
that it's a compelling use case for changing what __FILE__ does.

- Jonathan M Davis

Re: Building phobos GDC

[Lodovico Giaretta via Digitalmars-d-learn]

On Friday, 22 July 2016 at 20:26:50 UTC, Rufus Smith wrote:
On Friday, 22 July 2016 at 19:52:59 UTC, Lodovico Giaretta 
wrote:

On Friday, 22 July 2016 at 18:30:13 UTC, Rufus Smith wrote:
Trying to compile code that uses GDC, had to import phobos 
files from dmd in to project since they are not in the GDC's 
phobo lib(the core.sys.windows stuff).


Almost all the errors are related to stuff like

PALETTEENTRY* peNew() return { return _peNew.ptr; }


Does that even make sense?


I'll add that, in general, it's a bad idea to mix the 
libraries of the various compilers. In fact, the library has 
the same release cycle as the frontend, and is specific to the 
frontend version it comes with. GDC is several frontend 
versions behind DMD, so GDC cannot support the new features / 
characteristics of the recent DMD libraries.
You should always use a Phobos version as old as the frontend 
of the compiler you're using.


I don't agree with this. The versions are too far out of sync. 
It is better to test the different versions together because 
they are not consistent. As I yet I can neither use GDC or LDC 
because they don't compile the code that works with DMD. This 
is a problem with those compilers. If one could guarantee that 
the oldest compiler was always compatible, 
eventually(reasonably), with the newest one, it would be a 
different story. But bugs creep in. I'd rather work with the 
reference compiler, the actual one the language is based off 
of, rather than work with one that is not even guaranteed to be 
maintained properly.


With dmd, I know exactly what I'm getting and I only bother 
with the other compilers due to performance, which is not 
priority when developing. Hence, I hope that the other 
compilers are up to speed once I am finished with developing. 
This is a risk, but no more than expecting those compilers to 
eventually be updated. Given that the maintenance of LDC and 
GDC are rather low compared to DMD, I'd rather stick with DMD.


LDC is fairly up to date. In fact, it recently shipped an alpha 
version with support for the 2.071 frontend, while DMD 2.072 is 
still in beta. So, not that bad, just one version behind. I 
started a project a couple months ago with DMD 2.071. I'm still 
working on it, and now I can also use LDC.

The real problem is GDC, which apparently is currently at 2.066.

Re: Building phobos GDC

[Rufus Smith via Digitalmars-d-learn]

On Friday, 22 July 2016 at 19:52:59 UTC, Lodovico Giaretta wrote:

On Friday, 22 July 2016 at 18:30:13 UTC, Rufus Smith wrote:
Trying to compile code that uses GDC, had to import phobos 
files from dmd in to project since they are not in the GDC's 
phobo lib(the core.sys.windows stuff).


Almost all the errors are related to stuff like

PALETTEENTRY* peNew() return { return _peNew.ptr; }


Does that even make sense?


I'll add that, in general, it's a bad idea to mix the libraries 
of the various compilers. In fact, the library has the same 
release cycle as the frontend, and is specific to the frontend 
version it comes with. GDC is several frontend versions behind 
DMD, so GDC cannot support the new features / characteristics 
of the recent DMD libraries.
You should always use a Phobos version as old as the frontend 
of the compiler you're using.


I don't agree with this. The versions are too far out of sync. It 
is better to test the different versions together because they 
are not consistent. As I yet I can neither use GDC or LDC because 
they don't compile the code that works with DMD. This is a 
problem with those compilers. If one could guarantee that the 
oldest compiler was always compatible, eventually(reasonably), 
with the newest one, it would be a different story. But bugs 
creep in. I'd rather work with the reference compiler, the actual 
one the language is based off of, rather than work with one that 
is not even guaranteed to be maintained properly.


With dmd, I know exactly what I'm getting and I only bother with 
the other compilers due to performance, which is not priority 
when developing. Hence, I hope that the other compilers are up to 
speed once I am finished with developing. This is a risk, but no 
more than expecting those compilers to eventually be updated. 
Given that the maintenance of LDC and GDC are rather low compared 
to DMD, I'd rather stick with DMD.

Re: Building phobos GDC

[Lodovico Giaretta via Digitalmars-d-learn]

On Friday, 22 July 2016 at 18:30:13 UTC, Rufus Smith wrote:
Trying to compile code that uses GDC, had to import phobos 
files from dmd in to project since they are not in the GDC's 
phobo lib(the core.sys.windows stuff).


Almost all the errors are related to stuff like

PALETTEENTRY* peNew() return { return _peNew.ptr; }


Does that even make sense?


I'll add that, in general, it's a bad idea to mix the libraries 
of the various compilers. In fact, the library has the same 
release cycle as the frontend, and is specific to the frontend 
version it comes with. GDC is several frontend versions behind 
DMD, so GDC cannot support the new features / characteristics of 
the recent DMD libraries.
You should always use a Phobos version as old as the frontend of 
the compiler you're using.

Re: Building phobos GDC

[Lodovico Giaretta via Digitalmars-d-learn]

On Friday, 22 July 2016 at 18:30:13 UTC, Rufus Smith wrote:
Trying to compile code that uses GDC, had to import phobos 
files from dmd in to project since they are not in the GDC's 
phobo lib(the core.sys.windows stuff).


Almost all the errors are related to stuff like

PALETTEENTRY* peNew() return { return _peNew.ptr; }


Does that even make sense?


The peculiarity of this code is that it uses DIP 25.
I don't know if GDC supports it, nor if you need some compiler 
switch.

In DMD you need the -dip25 switch.

For more infos on DIP 25: https://wiki.dlang.org/DIP25

Re: full path to source file __FILE__

[Jonathan Marler via Digitalmars-d-learn]

On Friday, 22 July 2016 at 19:23:30 UTC, Steven Schveighoffer 
wrote:

On 7/22/16 2:43 PM, Kagamin wrote:

On Friday, 22 July 2016 at 13:50:55 UTC, Jonathan Marler wrote:

shell/anypath> rdmd /somedir/clean.d
Removing /somedir/build...


So for command rdmd /somedir/clean.d what __FILE__ contains? 
LDC tells
me the same path as specified on the command line, and that is 
specified

relative to current directory, where the compiler is called, so
absolutePath(__FILE__) should give the right result.


The issue which is not being expressed completely by Jonathan, 
is that rdmd caches the build.


So if I run the script from one directory, then cd elsewhere, 
it has the same __FILE__ as before, but the cwd has moved. So 
it won't work.


I had assumed rdmd would rebuild, but it doesn't.

-Steve


Thanks for pointing this out, somehow I overlooked this use case.

Re: full path to source file __FILE__

[Jonathan Marler via Digitalmars-d-learn]

On Friday, 22 July 2016 at 19:13:31 UTC, sdhdfhed wrote:

On Friday, 22 July 2016 at 14:02:03 UTC, Jonathan Marler wrote:
The __FILE__ trait seems to be used most useful for error 
messages.


Another usage is for testing parsers or string functions 
directly on the source. E.g in "devel" mode the main function


void main(string[] args)
{
version(devel)
{
// dont mess with params, use the text in source to 
catch most simple bugs.

File f = File(__FILE__, "r");
}
else
{
// load using args
}
}

I could see him wanting it to be a relative path sometimes and 
an absolute one other times.  By redefining it to always be 
absolute would solve this problem,


I'm for this, always absolute. Eventually forced by a new 
switch: default behavior is not changed.


Actually I realized if __FILE__ was always absolute, then all 
your exception messages would contain the full path of the file 
it was thrown from on the machine it was compiled on. This would 
be quite odd. Both a relative and absolute version are useful in 
different cases.

Re: full path to source file __FILE__

[Steven Schveighoffer via Digitalmars-d-learn]

On 7/22/16 2:43 PM, Kagamin wrote:

On Friday, 22 July 2016 at 13:50:55 UTC, Jonathan Marler wrote:

shell/anypath> rdmd /somedir/clean.d
Removing /somedir/build...


So for command rdmd /somedir/clean.d what __FILE__ contains? LDC tells
me the same path as specified on the command line, and that is specified
relative to current directory, where the compiler is called, so
absolutePath(__FILE__) should give the right result.


The issue which is not being expressed completely by Jonathan, is that 
rdmd caches the build.


So if I run the script from one directory, then cd elsewhere, it has the 
same __FILE__ as before, but the cwd has moved. So it won't work.


I had assumed rdmd would rebuild, but it doesn't.

-Steve

Re: full path to source file __FILE__

[sdhdfhed via Digitalmars-d-learn]

On Friday, 22 July 2016 at 14:02:03 UTC, Jonathan Marler wrote:
The __FILE__ trait seems to be used most useful for error 
messages.


Another usage is for testing parsers or string functions directly 
on the source. E.g in "devel" mode the main function


void main(string[] args)
{
version(devel)
{
// dont mess with params, use the text in source to catch 
most simple bugs.

File f = File(__FILE__, "r");
}
else
{
// load using args
}
}

I could see him wanting it to be a relative path sometimes and 
an absolute one other times.  By redefining it to always be 
absolute would solve this problem,


I'm for this, always absolute. Eventually forced by a new switch: 
default behavior is not changed.

Re: full path to source file __FILE__

[Kagamin via Digitalmars-d-learn]

On Friday, 22 July 2016 at 13:50:55 UTC, Jonathan Marler wrote:

shell/anypath> rdmd /somedir/clean.d
Removing /somedir/build...


So for command rdmd /somedir/clean.d what __FILE__ contains? LDC 
tells me the same path as specified on the command line, and that 
is specified relative to current directory, where the compiler is 
called, so absolutePath(__FILE__) should give the right result.

Building phobos GDC

[Rufus Smith via Digitalmars-d-learn]

Trying to compile code that uses GDC, had to import phobos files 
from dmd in to project since they are not in the GDC's phobo 
lib(the core.sys.windows stuff).


Almost all the errors are related to stuff like

PALETTEENTRY* peNew() return { return _peNew.ptr; }


Does that even make sense?

Re: full path to source file __FILE__

[Jonathan Marler via Digitalmars-d-learn]

On Friday, 22 July 2016 at 09:37:24 UTC, sdhdfhed wrote:

On Friday, 22 July 2016 at 08:36:37 UTC, Jonathan Marler wrote:

On Friday, 22 July 2016 at 07:57:35 UTC, sdhdfhed wrote:
On Friday, 22 July 2016 at 07:47:14 UTC, Jonathan Marler 
wrote:

On Friday, 22 July 2016 at 05:41:00 UTC, fdgdsgf wrote:

What's wrong with __FILE__.dirName ?


It's kinda weird, sometimes I've noticed that the __FILE__ 
keyword is an absolute path, and sometimes it isn't.  If it 
was always an absolute path, that would work.  I decided to 
take a stab at implementing this in the dmd compiler:


https://github.com/dlang/dmd/pull/5959

It adds a __FILE_FULL_PATH__ trait which would solve the 
issue.


Personally I've never seen a relative __FILE__. Is this an 
issue that's confirmed ?


I mean  that it would be better to fix __FILE__ so that its 
result is always absolute then. I think that such a "PPR" 
(punk-pull-request) has 0% chance of being accepted, 
especially since it adds a special keyword !


It's definitely confirmed.  And now that I've walked through 
the source code, I see that it wasn't implemented to be an 
absolute path, it just happens to be some of the time 
depending on how the file is found.  I'm sure Walter will have 
an opinion as to what solution he prefers.  Either redefining 
the __FILE__ trait or adding a new one. He's communicating 
fixes to the PR on github so that a good sign.  We'll see.


Yes, i've seen he 's started to review.

I don't know if you've seen my other suggestion but another 
solution would be to force relative fnames passed to the 
compiler to be translated to absolute. This is also why I've 
never seen a relative __FILE__. The build tool I use always 
does the expansion in intern before calling the compiler.


Again that's Walter's call.  The __FILE__ trait seems to be used 
most useful for error messages.  I could see him wanting it to be 
a relative path sometimes and an absolute one other times.  By 
redefining it to always be absolute would solve this problem, but 
might make others things harder.  I'm not particularly for or 
against either solution (not sure why you're trying to convince 
me of this one), that would be up to the owners of the language :)

Re: full path to source file __FILE__

[Jonathan Marler via Digitalmars-d-learn]

On Friday, 22 July 2016 at 13:30:10 UTC, Steven Schveighoffer 
wrote:

On 7/22/16 3:47 AM, Jonathan Marler wrote:

What's wrong with __FILE__.dirName ?


It's kinda weird, sometimes I've noticed that the __FILE__ 
keyword is an

absolute path, and sometimes it isn't.


If you combine it with current working directory, this should 
give you the full path.


Looks like std.path gives you a mechanism, I think this should 
work:


import std.path;
auto p = __FILE__.absolutePath;

http://dlang.org/phobos/std_path.html#.absolutePath

-Steve


That doesn't work in the example I provided:

/somedir/clean.d
/somedir/build

Say clean.d is meant to remove the build directory that lives in 
the same path as the clean.d script itself.


shell/anypath> rdmd /somedir/clean.d
Removing /somedir/build...

Since you are running the script from "anypath", the information 
that clean.d exists at /somedir is lost.  The last component to 
know where the file was found is the compiler itself.

Re: full path to source file __FILE__

[Steven Schveighoffer via Digitalmars-d-learn]

On 7/22/16 3:47 AM, Jonathan Marler wrote:

What's wrong with __FILE__.dirName ?


It's kinda weird, sometimes I've noticed that the __FILE__ keyword is an
absolute path, and sometimes it isn't.


If you combine it with current working directory, this should give you 
the full path.


Looks like std.path gives you a mechanism, I think this should work:

import std.path;
auto p = __FILE__.absolutePath;

http://dlang.org/phobos/std_path.html#.absolutePath

-Steve

Re: full path to source file __FILE__

[Adam D. Ruppe via Digitalmars-d-learn]

On Friday, 22 July 2016 at 10:51:57 UTC, Kagamin wrote:

Don't just ignore Adam's question :)


eh he answered it.

On Windows, it is somewhat common for things to be loaded or 
modified (especially on older versions when these were still 
writable...) from the program's directory. Its support files are 
all put together with the exe.


He's trying to make a "script" that is run with rdmd that 
pretends to work just like an exe and works with files around it.

JSON Serialization with runtime filtering.

[Alexander Milushev via Digitalmars-d-learn]

I there any json serialization library which allow to make 
decision about ignoring fields in runtime? I trying to write rest 
client but server accept either 'cmd' or 'args' field for example 
and I need to find solution.

Re: full path to source file __FILE__

[Kagamin via Digitalmars-d-learn]

On Friday, 22 July 2016 at 07:53:17 UTC, Jonathan Marler wrote:
It's important to remember that the clean.d script is ran with 
rdmd, and that it is meant to be called from any directory.  
Since it's ran with rdmd, the thisExePath won't give you the 
right directory, and since you can call it from any directory, 
you also can't use the current directory.  As you can see, what 
you really want to know is where the script itself lives.


Don't just ignore Adam's question :)
https://dlang.org/phobos/std_path.html#.absolutePath
https://dlang.org/phobos/std_file.html#.getcwd - why this won't 
work for you?

Re: full path to source file __FILE__

[sdhdfhed via Digitalmars-d-learn]

On Friday, 22 July 2016 at 08:36:37 UTC, Jonathan Marler wrote:

On Friday, 22 July 2016 at 07:57:35 UTC, sdhdfhed wrote:

On Friday, 22 July 2016 at 07:47:14 UTC, Jonathan Marler wrote:

On Friday, 22 July 2016 at 05:41:00 UTC, fdgdsgf wrote:

What's wrong with __FILE__.dirName ?


It's kinda weird, sometimes I've noticed that the __FILE__ 
keyword is an absolute path, and sometimes it isn't.  If it 
was always an absolute path, that would work.  I decided to 
take a stab at implementing this in the dmd compiler:


https://github.com/dlang/dmd/pull/5959

It adds a __FILE_FULL_PATH__ trait which would solve the 
issue.


Personally I've never seen a relative __FILE__. Is this an 
issue that's confirmed ?


I mean  that it would be better to fix __FILE__ so that its 
result is always absolute then. I think that such a "PPR" 
(punk-pull-request) has 0% chance of being accepted, 
especially since it adds a special keyword !


It's definitely confirmed.  And now that I've walked through 
the source code, I see that it wasn't implemented to be an 
absolute path, it just happens to be some of the time depending 
on how the file is found.  I'm sure Walter will have an opinion 
as to what solution he prefers.  Either redefining the __FILE__ 
trait or adding a new one. He's communicating fixes to the PR 
on github so that a good sign.  We'll see.


Yes, i've seen he 's started to review.

I don't know if you've seen my other suggestion but another 
solution would be to force relative fnames passed to the compiler 
to be translated to absolute. This is also why I've never seen a 
relative __FILE__. The build tool I use always does the expansion 
in intern before calling the compiler.

Re: union initalization

[Johannes Pfau via Digitalmars-d-learn]

Am Fri, 22 Jul 2016 01:48:52 +
schrieb Rufus Smith :

> I would like to combine two types
> 
> 
> template Foo(A, B = 4)
> {
>  union
>  {
> byte b = B;
> int a = A << 8;
>  }
> }
> 
> 
> I get an error about overlapping default initialization. They 
> don't actually overlap in this case because of the shift.

To be pedantic about this: The initializers actually do overlap. As A
<< 8 shifts in zeroes, these bits are initialized as well. I think
there's no idiomatic way to initialize only part of an integer.

Re: full path to source file __FILE__

[Jonathan Marler via Digitalmars-d-learn]

On Friday, 22 July 2016 at 07:57:35 UTC, sdhdfhed wrote:

On Friday, 22 July 2016 at 07:47:14 UTC, Jonathan Marler wrote:

On Friday, 22 July 2016 at 05:41:00 UTC, fdgdsgf wrote:

What's wrong with __FILE__.dirName ?


It's kinda weird, sometimes I've noticed that the __FILE__ 
keyword is an absolute path, and sometimes it isn't.  If it 
was always an absolute path, that would work.  I decided to 
take a stab at implementing this in the dmd compiler:


https://github.com/dlang/dmd/pull/5959

It adds a __FILE_FULL_PATH__ trait which would solve the issue.


Personally I've never seen a relative __FILE__. Is this an 
issue that's confirmed ?


I mean  that it would be better to fix __FILE__ so that its 
result is always absolute then. I think that such a "PPR" 
(punk-pull-request) has 0% chance of being accepted, especially 
since it adds a special keyword !


It's definitely confirmed.  And now that I've walked through the 
source code, I see that it wasn't implemented to be an absolute 
path, it just happens to be some of the time depending on how the 
file is found.  I'm sure Walter will have an opinion as to what 
solution he prefers.  Either redefining the __FILE__ trait or 
adding a new one. He's communicating fixes to the PR on github so 
that a good sign.  We'll see.

Re: full path to source file __FILE__

[sdhdfhed via Digitalmars-d-learn]

On Friday, 22 July 2016 at 07:57:35 UTC, sdhdfhed wrote:

On Friday, 22 July 2016 at 07:47:14 UTC, Jonathan Marler wrote:

[...]


Personally I've never seen a relative __FILE__. Is this an 
issue that's confirmed ?


I mean  that it would be better to fix __FILE__ so that its 
result is always absolute then. I think that such a "PPR" 
(punk-pull-request) has 0% chance of being accepted, especially 
since it adds a special keyword !


make a PR that expands the sources passed to the dmd to their 
absolute name. This is more likely to fix your issue and to be 
accepted.

Re: full path to source file __FILE__

[sdhdfhed via Digitalmars-d-learn]

On Friday, 22 July 2016 at 07:47:14 UTC, Jonathan Marler wrote:

On Friday, 22 July 2016 at 05:41:00 UTC, fdgdsgf wrote:

What's wrong with __FILE__.dirName ?


It's kinda weird, sometimes I've noticed that the __FILE__ 
keyword is an absolute path, and sometimes it isn't.  If it was 
always an absolute path, that would work.  I decided to take a 
stab at implementing this in the dmd compiler:


https://github.com/dlang/dmd/pull/5959

It adds a __FILE_FULL_PATH__ trait which would solve the issue.


Personally I've never seen a relative __FILE__. Is this an issue 
that's confirmed ?


I mean  that it would be better to fix __FILE__ so that its 
result is always absolute then. I think that such a "PPR" 
(punk-pull-request) has 0% chance of being accepted, especially 
since it adds a special keyword !

Re: full path to source file __FILE__

[Jonathan Marler via Digitalmars-d-learn]

On Friday, 22 July 2016 at 06:45:58 UTC, Jacob Carlborg wrote:

On 2016-07-22 04:24, Jonathan Marler wrote:

The script depends on other files relative to where it exists 
on the
file system.  I couldn't think of a better design to find 
these files

then knowing where the script exists, can you?


What kind of files are we talking about. Resource files, config 
files? Are they static? For static resource files you can 
bundle them in the executable with a string import. For config 
files it might be better to store it in a completely different 
directory, like the user's home directory. This actually 
depends on what kind of config files and the operating system.


I suppose I should have been more specific.  The script actually 
operates on the filesystem relative to where it lives.  It copies 
files, modifies directories, etc.  It is meant to be ran from any 
directory, but is only meant to modify the filesystem relative to 
where it lives.  Take a simple example of a clean script:


/somedir/clean.d
/somedir/build

Say clean.d is meant to remove the build directory that lives in 
the same path as the clean.d script itself.


shell/anypath> rdmd /somedir/clean.d
Removing /somedir/build...

It's important to remember that the clean.d script is ran with 
rdmd, and that it is meant to be called from any directory.  
Since it's ran with rdmd, the thisExePath won't give you the 
right directory, and since you can call it from any directory, 
you also can't use the current directory.  As you can see, what 
you really want to know is where the script itself lives.

Re: full path to source file __FILE__

[Jonathan Marler via Digitalmars-d-learn]

On Friday, 22 July 2016 at 05:41:00 UTC, fdgdsgf wrote:
On Thursday, 21 July 2016 at 19:54:34 UTC, Jonathan Marler 
wrote:
Is there a way to get the full path of the current source 
file? Something like:


__FILE_FULL_PATH__

I'm asking because I'm rewriting a batch script in D, meant to 
be ran with rdmd.  However, the script needs to know it's own 
path.  The original batch script uses the %~dp0 variable for 
this, but I'm at a loss on how to do this in D.  Since rdmd 
compiles the executable to the %TEMP% directory, thisExePath 
won't work.


BATCH
-
echo "Directory of this script is " %~dp0


DLANG
-
import std.stdio;
int main(string[] args) {
writeln("Directory of this script is ", ???);
}


What's wrong with __FILE__.dirName ?


It's kinda weird, sometimes I've noticed that the __FILE__ 
keyword is an absolute path, and sometimes it isn't.  If it was 
always an absolute path, that would work.  I decided to take a 
stab at implementing this in the dmd compiler:


https://github.com/dlang/dmd/pull/5959

It adds a __FILE_FULL_PATH__ trait which would solve the issue.

Re: full path to source file __FILE__

[Jacob Carlborg via Digitalmars-d-learn]

On 2016-07-22 04:24, Jonathan Marler wrote:


The script depends on other files relative to where it exists on the
file system.  I couldn't think of a better design to find these files
then knowing where the script exists, can you?


What kind of files are we talking about. Resource files, config files? 
Are they static? For static resource files you can bundle them in the 
executable with a string import. For config files it might be better to 
store it in a completely different directory, like the user's home 
directory. This actually depends on what kind of config files and the 
operating system.


--
/Jacob Carlborg

Re: union initalization

[Ali Çehreli via Digitalmars-d-learn]

On 07/21/2016 08:00 PM, Rufus Smith wrote:

>> Bitfields may actually be useful in this case:
>>
>>   https://dlang.org/phobos/std_bitmanip.html#.bitfields
>>
>
> They don't allow default assignment though?

A factory function can help:

import std.bitmanip;

struct S(int a_init, byte b_init) {
mixin (bitfields!(int, "a", 24,
  byte, "b", 8));
@disable this();
}

auto makeS(int a_init, byte b_init = 4)() {
auto s = S!(a_init, b_init).init;
s.a = a_init;
s.b = b_init;
return s;
}

void main() {
const s = makeS!42();
assert(s.a == 42);
assert(s.b == 4);
}

>> The following at least compiles:
>>
>> struct Foo(int A, byte B = 4)
>> {
>> union
>> {
>> byte b = void;
>> int a = void;
>> uint __both = (A << 8) | B;
>> }
>> }
>>
>> void main() {
>> auto f = Foo!(42)();
>> }
>>
>> Ali
>
> Maybe... I don't like extra member.

Me neither. Besides, 'b' coincides with a different part of 'a' 
depending on the endianness of the system.


Ali