• lurker (7/7) Jun 02 2008 hi,
• BCS (9/23) Jun 02 2008 first, classes are reference types so the above needs to be:
• Koroskin Denis (28/35) Jun 02 2008 You shouldn't use this for by design, it's not supported for reference
• BCS (3/28) Jun 02 2008 It's not really clean but making a dup() method would be constant with D...

lurker <lurker lurker.com> writes:

hi,

i like to copy objects such as:

class A {....}

A xxx; // some things are done ...

A yyy = xxx;

how can one do that in D2 easy? are any samples?

thanks

BCS <ao pathlink.com> writes:

Reply to lurker,

 hi,
 
 i like to copy objects such as:
 
 class A {....}
 
 A xxx; // some things are done ...
 
 A yyy = xxx;
 
 how can one do that in D2 easy? are any samples?
 
 thanks
 

first, classes are reference types so the above needs to be:

A xxx = new A;
 // some things are done ...
A yyy = xxx;

second, that assignment will work as is but will act as a reference copy 
(you get two copies of the reference to the same object). If you want a real 
copy you can use structs or generate a deep copy function for the class. 
I don't use 2.0 so someone else will need to fill in the details.

"Koroskin Denis" <2korden gmail.com> writes:

On Mon, 02 Jun 2008 20:08:29 +0400, lurker <lurker lurker.com> wrote:

 hi,

 i like to copy objects such as:

 class A {....}

 A xxx; // some things are done ...

 A yyy = xxx;

 how can one do that in D2 easy? are any samples?

 thanks

You shouldn't use this for by design, it's not supported for reference  
types, only for structs.
But you might consider wrapping the class into a struct with overloaded  
opAssign semantics.
It sould work fine for you (after opImplicitCast is implemented :)).

The other limitation of opAssign is that you can't override opAssign to  
accept object of the same type:

T t1;
T t2;
t1 = t2; // can't be hooked :(

Compiler just makes a plain bitwise copy of the object in any case.

I was trying to implement C++-style reference (Ref!(T) template), it works  
fine but the I didn't find any way to disallow reference rebindment:

int i = 5;
Ref!(int) ri = i;

ri = 0;
assert(ri == i);

--ri;
assert(ri == i);

ri *= 2;
assert(ri == i);

ri ^= 4;
assert(ri == i);

int t = 0;

ri = Ref!(int)(&t);	// that's what I want to disallow, but can't :(
assert(ri == i);

Anyone knows how to workaround this?

BCS <ao pathlink.com> writes:

Reply to Koroskin,

 On Mon, 02 Jun 2008 20:08:29 +0400, lurker <lurker lurker.com> wrote:
 
 hi,
 
 i like to copy objects such as:
 
 class A {....}
 
 A xxx; // some things are done ...
 
 A yyy = xxx;
 
 how can one do that in D2 easy? are any samples?
 
 thanks
 

 You shouldn't use this for by design, it's not supported for reference
 types, only for structs.
 But you might consider wrapping the class into a struct with
 overloaded
 opAssign semantics.
 It sould work fine for you (after opImplicitCast is implemented :)).
 The other limitation of opAssign is that you can't override opAssign
 to  accept object of the same type:
 

It's not really clean but making a dup() method would be constant with D's 
arrays.