• mark (6/6) Mar 04 2020 In Adam Ruppe's D Cookbook there're these lines in a ref counting
• drug (3/10) Mar 05 2020 In D all vars are initialized by default. If you use assigning void then...
• Simen =?UTF-8?B?S2rDpnLDpXM=?= (16/28) Mar 05 2020 To expand a bit on this: You probably don't want to initialize
• mark (3/15) Mar 05 2020 Thanks, I had read it (in "Learning D" I think), but had already

mark <mark qtrac.eu> writes:

In Adam Ruppe's D Cookbook there're these lines in a ref counting 
example:

RefCountedObject o = void; // What does this mean/do?
o.data = new Implementation();
o.data.refcount = 1;

I don't understand the first line; could someone explain please?

drug <drug2004 bk.ru> writes:

On 3/5/20 10:47 AM, mark wrote:
 In Adam Ruppe's D Cookbook there're these lines in a ref counting example:
 
 RefCountedObject o = void; // What does this mean/do?
 o.data = new Implementation();
 o.data.refcount = 1;
 
 I don't understand the first line; could someone explain please?


In D all vars are initialized by default. If you use assigning void then 
the var won't be initialized.

Simen =?UTF-8?B?S2rDpnLDpXM=?= <simen.kjaras gmail.com> writes:

On Thursday, 5 March 2020 at 08:35:52 UTC, drug wrote:
 On 3/5/20 10:47 AM, mark wrote:
 In Adam Ruppe's D Cookbook there're these lines in a ref 
 counting example:
 
 RefCountedObject o = void; // What does this mean/do?
 o.data = new Implementation();
 o.data.refcount = 1;
 
 I don't understand the first line; could someone explain 
 please?


 In D all vars are initialized by default. If you use assigning 
 void then the var won't be initialized.

To expand a bit on this: You probably don't want to initialize 
things with = void - it can lead to hard-to-track bugs and 
unexpected behavior. The reasons it's there is almost entirely as 
an optimization - if you know the variable will be initialized 
elsewhere void initialization ensure things won't be initialized 
twice when once is enough, and this can be faster.

The other use case is when for whatever reason there is no valid 
default value, but you still want an instance. Probably in order 
to fill it with data from somewhere else. This would apply e.g. 
to structs with  disabled parameterless constructors whose 
contents you are reading from disk.

In short, when you know you need to void initialize something, 
that's when you're ready to use it. Kinda like goto.

--
   Simen

mark <mark qtrac.eu> writes:

On Thursday, 5 March 2020 at 08:35:52 UTC, drug wrote:
 On 3/5/20 10:47 AM, mark wrote:
 In Adam Ruppe's D Cookbook there're these lines in a ref 
 counting example:
 
 RefCountedObject o = void; // What does this mean/do?
 o.data = new Implementation();
 o.data.refcount = 1;
 
 I don't understand the first line; could someone explain 
 please?


 In D all vars are initialized by default. If you use assigning 
 void then the var won't be initialized.

Thanks, I had read it (in "Learning D" I think), but had already 
forgotten.