• Heinz <malagana15 yahoo.es> Apr 27 2008
• downs <default_357-line yahoo.de> Apr 28 2008
• Heinz <malagana15 yahoo.es> Apr 28 2008
• "Simen Kjaeraas" <simen.kjaras gmail.com> Apr 28 2008
• downs <default_357-line yahoo.de> Apr 29 2008

Hi,

I have a simple struct and i want to check if a variable has been asigned:

struct hello
{

}
...
hello h;
...
if(!h)
{
do stuff;
}

When compiling i get erros about opCall not implemented and many others. What
can i do?

Thanks in advance.

Heinz wrote:
 Hi,
 
 I have a simple struct and i want to check if a variable has been asigned:
 
 struct hello
 {
 
 }
 ...
 hello h;
 ...
 if(!h)
 {
 do stuff;
 }
 
 When compiling i get erros about opCall not implemented and many others. What
can i do?
 
 Thanks in advance.


Structs are value types. Read the spec. Then use a pointer :)

hello* h;

if (!h) h = new hello;

 --downs

downs Wrote:

 Heinz wrote:
 Hi,
 
 I have a simple struct and i want to check if a variable has been asigned:
 
 struct hello
 {
 
 }
 ...
 hello h;
 ...
 if(!h)
 {
 do stuff;
 }
 
 When compiling i get erros about opCall not implemented and many others. What
can i do?
 
 Thanks in advance.


 Structs are value types. Read the spec. Then use a pointer :)
 
 hello* h;
 
 if (!h) h = new hello;
 
  --downs


Thanks for your reply. Can i use then?:
 hello h;
if(!&h)

On Tue, 29 Apr 2008 06:50:18 +0200, Heinz <malagana15 yahoo.es> wrote:

 downs Wrote:
 Structs are value types. Read the spec. Then use a pointer :)

 hello* h;

 if (!h) h =3D new hello;

  --downs


 Thanks for your reply. Can i use then?:
  hello h;
 if(!&h)



No. &h will always return a non-null pointer (h exists, in other words).=


You might use some convoluted workaround to make hello aware of whether =
or
not it has been assigned something.

Easy example:

struct hello
{
   bool assigned;
   // other fields;
}

hello h;

h =3D hello(true, ...);

if (h.assigned)
   DoSomethingOrOther();


This may or may not be enough for you needs.

-- Simen

Heinz wrote:
 downs Wrote:
 
 Heinz wrote:
 Hi,

 I have a simple struct and i want to check if a variable has been asigned:

 struct hello
 {

 }
 ...
 hello h;
 ...
 if(!h)
 {
 do stuff;
 }

 When compiling i get erros about opCall not implemented and many others. What
can i do?

 Thanks in advance.



 hello* h;

 if (!h) h = new hello;

  --downs


 Thanks for your reply. Can i use then?:
  hello h;
 if(!&h)


No.
Structs are *value types*.

That means, unless _explicitly newed_ (or part of a struct that's explicitly
newed), they _always_ live on the stack.

Ergo, if &h is null, your complete callstack is shot :)

 --downs