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));
    }
}
void thefun(pt1 x){
    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));
    }
}

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?
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

I believe that pt1(r) value is created on the stack, then the thefunc is called with that value (by Value semantic - so another value is created on the stack) and it prints pointer to the value on the stack. Then it returnes so the stack values are destroyed, next iteration begins and all steps are the same. The addresses of the values are just the same as thay were in previous loop. calling the function is deterministic so the addresses are also because nothing else stays on the stack between two iterations.
On 23.12.2010 00:16, 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));
>      }
> }
> void thefun(pt1 x){
>      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));
>      }
> }
>
> 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?
> 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

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