Copying structs via function (not bitwise)

[Matthias Walter]

Bill Baxter Wrote:

> Matthias Walter wrote:
> > Is there any other way of copying structs with '=' operator, other than the default way of a bitwise copy? I quote the FAQ:
> > 
> > "Structs, being value objects, do get copied about. A copy is defined in D to be a bit copy. I've never been comfortable with any object in C++ that does something other than a bit copy when copied. Most of this other behavior stems from that old problem of trying to manage memory. Absent that, there doesn't seem to be a compelling rationale for having anything other than a bit copy."
> > 
> > The reason, I'm asking for this, is that I'm working on a GMP port. Because numbers _must_ be value types, I must use structs. But as different instances of the same number must reference another memory region of the GMP internals, I must call special copy functions, if I do "a = b;" on two gmp-structs, a refers to the same gmp-internal memory as b.
> > 
> > Is there any way to do this?
> > 
> > best regards
> > Matthias Walter
> 
> opAssign can be used to override the meaning of A=B where A and B are 
> different types.  But by design you can't change the meaning A=B where A 
> and B are the same type.
> 
> But you could make it work using any of the following:
> 
> A ~= B;
> A.foo = B;
> A = B.foo;
> assign(A,B);
> A.assign(B);
> etc..
> 
> And I'm sure downs could suggest a few more workable syntaxes. :-)
> 
> --bb

Problem is that GMP-structs should behave like normal numbers and one also does not write:
int i;
i.value = 10;

Does this mean, that in the current situation, it is impossible to port the GMP library with structs so that 

T i,j = 0;
i = j;
j++;
assert (i == 0);

works for T = int, T = long, T = float, T = gmp_struct ?

best regards
Matthias Walter