Testing some pointer basics

Ref_basics.dpr

{$APPTYPE CONSOLE}
program Nulls_in_Delphi;
uses
  System.SysUtils;

const nl = sLineBreak;

procedure print(a:pointer;b:longint; s:string);
begin
  writeln(  longint(a).ToHexString, '   ',  b.ToHexString, '   ', s);
end;


type
  Tmyrecord = record
     s:string
  end;

  Tmyclass = class
     s:string
  end;

var i:integer;
    s:string;
    c:Tmyclass;
    r:Tmyrecord;

begin
   writeln;

//   var i:integer;
//   var s:string;
//   var c:Tmyclass;
//   var r:Tmyrecord;

   print( @i, longint(i), 'int');
   print( @s, longint(s), 'str');
   print( @r, longint(r), 'rec');
   print( @c, longint(c), 'class');

   writeln(nl,'string');
   s := 'abc';
   print( @s, longint(s), s);
   s := '';
   print( @s, longint(s), '"');

   writeln(nl,'record');
   print( @r, longint(r), '');
   r.s := 'abc';
   print( @r, longint(r), r.s);
   r.s := 'abcd';
   print( @r, longint(r), r.s);

   writeln(nl,'class');
   c := Tmyclass.Create;
   print( @c.s, longint(c.s), '');
   c.s := 'abc';
   print( @c.s, longint(c.s), c.s);
   c.s := 'abcd';
   print( @c.s, longint(c.s), c.s);


   // if c?.s?.length > 0 then ...

   // c   := nil;   // to test short-circuiting
   // c.s := '' ;
   // c.s := ' ';

   if assigned(c)     then
   if (c.s<>'')       then
   if (length(c.s)>0) then  writeln(nl,length(c.s));

   if assigned(c) and (c.s<>'') and (length(c.s)>0) then writeln(nl,length(c.s));

   readln;
end.