is this the expected output

[Dmitry Olshansky]

On 23.12.2010 2:16, g g wrote:
> Is this code :
>
> import std.stdio;
> import std.conv;
> struct pt1{
>      p val;
>      pt1* next;
> }
> struct p{
>      int val;
>      string toString(){
>          return(to!string(val));
>      }
> }

Here, notice that thefun is taking pt1 by value - a copy.

> void thefun(pt1 x){
>      writeln(&x);
> }
Then you take address of local copy, which is unacceptable. What you 
probably wanted is this:

void thefun(ref pt1 x){//reference to the original , but then it must be lvalue
     writeln(&x);
}

> void main(){
>      auto p0 = p(1);
>      auto p1 = p(2);
>      auto p2 = p(3);
>      auto p3 = p(4);
>      p[] arr = [p0,p1,p2,p3];
>      writeln(arr);
>      foreach(r;arr){
>          thefun(pt1(r));
>      }
> }

But here you pass a rvalue to function that takes address. In fact, it 
prints the address of temporary place in  stack used to hold result of 
pt1(r).
> supposed to output this:
>
> 1 2 3 4
> BFE61E28
> BFE61E28
> BFE61E28
> BFE61E28 //Note all the addresses are the same
>
> It is expected that using a  struct literal(or default constructor) on a bucle reuses the same address?
Yes, inside loop it's likely to use the same address, but actually you 
didn't took it but an address of a copy of it ;)  Which means you need 
to store these temporaries like pt1(r) somewhere, usually on heap (just 
as you do with dynamic array of p).
> I got hit by this trying to do a tree structure builder, for hours searching aand finally found this (feature | bug). If so, how I could get a new struct to void changing (in a unnoticeable way) the same struct i just set.
>
> thanks.
> g g

-- 
Dmitry Olshansky