I thought it'd be a good idea to set global immutables from args passed to main().  When I do this:


import io = std.stdio;

immutable string abc;

void foo() {
  io.writeln(abc);
}

void main(string[] args) {
  abc = args[1];
  foo();
}


...I get the compiler error: "Error: can only initialize const member abc inside constructor".  When I do this:


import io = std.stdio;

void foo() {
  io.writeln(abc);
}

void main(string[] args) {
  immutable string abc = args[1];
  foo();
}


...I get the compiler error: "Error: undefined identifier abc".

Is there any workaround, or am I attempting a stupidity/impossibility?

Thanks.

Andrew

On Tuesday, 28 January 2014 at 17:11:43 UTC, Andrew Klaassen wrote:

Naturally, initialize them in constructor :)

http://dpaste.dzfl.pl/620e8c61

On Tue, 28 Jan 2014 12:27:02 -0500, Stanislav Blinov <stanislav.blinov@gmail.com> wrote:

> On Tuesday, 28 January 2014 at 17:11:43 UTC, Andrew Klaassen wrote:
>
> Naturally, initialize them in constructor :)
>
> http://dpaste.dzfl.pl/620e8c61

That being said, it *could* be done, since the runtime has access to the command line args. But the runtime would have to provide access to those parameters. But you'd have to do it in a static constructor.

-Steve

On Tuesday, 28 January 2014 at 18:30:37 UTC, Steven Schveighoffer wrote:
> On Tue, 28 Jan 2014 12:27:02 -0500, Stanislav Blinov <stanislav.blinov@gmail.com> wrote:
>>
>> http://dpaste.dzfl.pl/620e8c61
>
> That being said, it *could* be done, since the runtime has access to the command line args. But the runtime would have to provide access to those parameters. But you'd have to do it in a static constructor.
>

Ahem. There was a link to dpaste :D

On Tue, 28 Jan 2014 13:41:24 -0500, Stanislav Blinov <stanislav.blinov@gmail.com> wrote:

> On Tuesday, 28 January 2014 at 18:30:37 UTC, Steven Schveighoffer wrote:
>> On Tue, 28 Jan 2014 12:27:02 -0500, Stanislav Blinov <stanislav.blinov@gmail.com> wrote:
>>>
>>> http://dpaste.dzfl.pl/620e8c61
>>
>> That being said, it *could* be done, since the runtime has access to the command line args. But the runtime would have to provide access to those parameters. But you'd have to do it in a static constructor.
>>
>
> Ahem. There was a link to dpaste :D

Oops! I glossed over that :) I thought the example just showed how a static constructor was required to initialize, I didn't see the access to the program args.

-Steve

On 01/28/2014 10:41 AM, Stanislav Blinov wrote:
> On Tuesday, 28 January 2014 at 18:30:37 UTC, Steven Schveighoffer wrote:
>> On Tue, 28 Jan 2014 12:27:02 -0500, Stanislav Blinov
>> <stanislav.blinov@gmail.com> wrote:
>>>
>>> http://dpaste.dzfl.pl/620e8c61
>>
>> That being said, it *could* be done, since the runtime has access to
>> the command line args. But the runtime would have to provide access to
>> those parameters. But you'd have to do it in a static constructor.
>>
>
> Ahem. There was a link to dpaste :D

On a side note, dpaste is not associated with newsgroups. It can disappear at any time in the future. I like seeing and showing code in message bodies both for convenience and future availability. :)

Ali

On Tuesday, 28 January 2014 at 18:56:35 UTC, Ali Çehreli wrote:

> On a side note, dpaste is not associated with newsgroups. It can disappear at any time in the future. I like seeing and showing code in message bodies both for convenience and future availability. :)

Awww, but it is so much more convenient. No spurious linebreaks, nice syntax highlighting, built-in compiler... :P

But I agree, sometimes it's a real pain when you've searching for something and all you find is dead links.

On Tuesday, 28 January 2014 at 19:02:41 UTC, Stanislav Blinov wrote:
> On Tuesday, 28 January 2014 at 18:56:35 UTC, Ali Çehreli wrote:
>
>> On a side note, dpaste is not associated with newsgroups. It can disappear at any time in the future. I like seeing and showing code in message bodies both for convenience and future availability. :)
>
> Awww, but it is so much more convenient. No spurious linebreaks, nice syntax highlighting, built-in compiler... :P
>
> But I agree, sometimes it's a real pain when you've searching for something and all you find is dead links.

Cutting and pasting for posterity... :-)


import std.stdio;
import core.runtime;

immutable string abc;

void main() {
	writeln(abc);
}

shared static this() {
	alias args = Runtime.args;
	if (args.length > 1)
		abc = args[1];
}


Fascinating.  Any chance someone would be able to add this to http://dlang.org/module.html as an example for people like me who'd have no clue otherwise?

Andrew

On Tuesday, 28 January 2014 at 20:07:25 UTC, Andrew Klaassen wrote:

> Fascinating.  Any chance someone would be able to add this to http://dlang.org/module.html as an example for people like me who'd have no clue otherwise?

Initialization of immutable globals is actually in the docs: http://dlang.org/const3.html. It's a third example in "Immutable Storage Class". ;)

On Tuesday, 28 January 2014 at 19:02:41 UTC, Stanislav Blinov wrote:
> On Tuesday, 28 January 2014 at 18:56:35 UTC, Ali Çehreli wrote:
>
>> On a side note, dpaste is not associated with newsgroups. It can disappear at any time in the future. I like seeing and showing code in message bodies both for convenience and future availability. :)
>
> Awww, but it is so much more convenient. No spurious linebreaks, nice syntax highlighting, built-in compiler... :P
>
> But I agree, sometimes it's a real pain when you've searching for something and all you find is dead links.

You can also use the Github Gist feature for displaying code, can't you?