Record "inheritance"/structuring

[quantumfoam]

Is it possible to somehow write composite records to simplify record definition like this?

Code: Pascal  [Select][+][-]

1. type rec1 = record
2.   a:integer; // offset 0, length 4 bytes
3. end;
4.  
5. type rec2 = record(rec1) // does not compile
6.   b:integer; // offset 4, length 4 bytes
7. end;
8.  
9. var x:rec2;
10.  
11. begin
12.   x.a := 1;
13.   x.b := 2;
14. end.
15.  

[MarkMLl]

Use a class.

MarkMLl

[quantumfoam]

@MarkMLl. This would be too slow for my purposes, since each object needs a create call. I need to allocate many of such records into pages, and access them via pointers.
EDIT: Also, I don't need any methods/functions attached to these records. Just plain data.

[HeavyUser]

@MarkMLl. This would be too slow for my purposes, since each object needs a create call. I need to allocate many of such records into pages, and access them via pointers.

use objects then
a quick feature comparison
https://wiki.freepascal.org/Record#Records_compared_to_other_structured_types

[quantumfoam]

@HeavyUser, thanks. I didn't know about Object, I only used Classes before. And I didn't know that class can be "created" via New keyword. Anyway, since Objects can be created in arrays without instantion/creation of every single instance (contrary to Classes), I'll use Objects.

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. type rec2 = record
6.   a,b,c:integer;
7. end;
8. type prec2 = ^rec2;
9.  
10. type obj1 = object
11.   a,b:integer;
12. end;
13.  
14. type obj2 = object(obj1)
15.   c:integer;
16.   procedure add;
17. end;
18. type pobj2 = ^obj2;
19.  
20. type cls1 = class
21.   a,b:integer;
22. end;
23. type cls2 = class(cls1)
24.   c:integer;
25.   procedure add;
26. end;
27. type pcls2 = ^cls2;
28.  
29.  
30. procedure obj2.add;
31. begin
32.   c := c + 4;
33. end;
34.  
35. procedure cls2.add;
36. begin
37.   c := c + 4;
38. end;
39.  
40. var o:pobj2; c:pcls2;
41.   page:array of obj2;
42.   i:integer;
43.   const cnt = 3;
44.  
45.  
46.  
47. begin
48.   writeln(sizeof(rec2)); // 12
49.   writeln(sizeof(obj2)); // 12
50.   writeln(sizeof(cls2)); // 4
51.   setlength(page, cnt);
52.   for i := 0 to cnt - 1 do begin
53.     page[i].c := i;
54.     page[i].add;
55.     writeln(page[i].c);
56.   end;
57.   //new(o);
58.   //new(c);
59. end.
60.  

[PascalDragon]

And I didn't know that class can be "created" via New keyword.

• Classes can not be instantiated via New, they are only instantiated by using a constructor
• New is not a keyword; it's an intrinsic and works on any typed pointer variable