On Friday, 13 June 2014 at 15:05:49 UTC, Tom Browder via Digitalmars-d-learn wrote:
> So I'm not sure how to translate that into D.   I do know my first
> attempt here doesn't work, even with it being surrounded by extern (C)
> {}:
>
> $ cat chdr.d
> struct t;
> struct t* t_ptr = null;

This seems to work fine for me. What's the problem?

Note this isn't *strictly* the same as what you have in C, as "null" is not strongly bindded to a single type. If you want a null pointer which is pre-emptivelly strongly, then you can use an eponymous template:

enum nullptr(T) = (T*).init;

auto p = nullptr!t;

Throw in an alias, and you got it working exactly like an C:


enum nullptr(T) = (T*).init;
alias t_nullptr = nullptr!t;
struct t* t_ptr = t_nullptr;

That said, I'd advise against this. Just use "null" and move on. It's idiomatic.

On Fri, Jun 13, 2014 at 10:15 AM, monarch_dodra via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com> wrote:
> On Friday, 13 June 2014 at 15:05:49 UTC, Tom Browder via Digitalmars-d-learn wrote:
>>
>> So I'm not sure how to translate that into D.   I do know my first attempt here doesn't work, even with it being surrounded by extern (C) {}:
>>
>> $ cat chdr.d
>> struct t;
>> struct t* t_ptr = null;
>
>
> This seems to work fine for me. What's the problem?

I use "dmd -c .d" (note file name change) and get:

t.d(2): Error: { } expected following aggregate declaration
t.d(2): Error: Declaration expected, not '*'

Taking Philpax's  suggestion I try

$ cat t.d
struct t;
t* t_ptr = null;

$ dmd -c t.d

and get a good build.

> Note this isn't *strictly* the same as what you have in C, as "null" is not
...
> strongly bindded to a single type. If you want a null pointer which is pre-emptivelly strongly, then you can use an eponymous template:
...
> That said, I'd advise against this. Just use "null" and move on. It's idiomatic.

So this is the correct (i.e., good enough) solution then:

$ cat t.d
struct t;
t* t_ptr = null;

Sounds good to me.

Thanks all.

Best,

-Tom