member func is best choice for pointers?

[Salih Dincer]

On Thursday, 6 April 2023 at 14:26:01 UTC, a11e99z wrote:
> member func has invariant that **this** is not null (programmer 
> thinks so).
> global func hasn't the one and programmer should check for it 
> before doing something ...

I understand what you mean.  When you try to access the last node 
of a linked list, you will get the segmentation fault if you are 
using a built-in viewer (toString).  For example:

```d
struct Node
{
   int item;
   Node * back;

   string toString()
   {
     import std.format : format;

     return format("Node::%s (back)-> %s", item,
                                      back.item);
   }
}

void main()
{
   import std.stdio : writeln;

   auto node1 = Node(41);
   auto node1Ptr = &node1;

   //printNode(node1Ptr);/* NOT COMPILE!
   node1.writeln;//* Main::41 (back)-> null */

   auto node2 = Node(42);
   node2.back = node1Ptr;

   printNode(&node2); // Main::42 (back)-> 41
   node2.writeln;     // Node::42 (back)-> 41
}

void printNode(Node * p)
{
   import std.stdio : writefln;

   if(p.back is null)
   {
     writefln("Main::%s (back)-> null", p.item);
   } else {
     writefln("Main::%s (back)-> %s", p.item,
                                 p.back.item);
   }
}
```

If you don't remove the comment line (just remove the // sign: 
toggle-comment) the above code will not compile.  Because it is 
not connect to any node.

@SDB