Help topic for 'Generics', template list

[AlexTP]

https://www.freepascal.org/docs-html/current/ref/refse53.html
This tells us that 'template list' may contain 'identifier : typeId ; identifier2 : tideId2'. But no examples for that! Examples only show very simple template list. Pls give an example for complex template list.

[Warfley]

I think this mostly refers to the type constraints

Code: Pascal  [Select][+][-]

1. generic TTest<T: TObject> = …

this can only be a class (I.e. inherits from TObject)
The reason you have ; is probably because , is for having multiple of the same type like "A, B: TObject" which makes both A And B require to be a class vs "A; B: TObject" which makes A unrestricted and B a class

I think on the trunk there is also the feature for constants:

Code: Pascal  [Select][+][-]

1. generic TBuffer<const Size: SizeInt> …
2.  
3. T1KBuff = specialize TBuffer<1024>

But I’m not sure right now if I remember correctly

But yes, this definitely needs some documentation, I figured that stuff out a year ago or so simply by trial and error, just trying out various constructs that I thought could work, and surprisingly many of them worked (at least on trunk)

[AlexTP]

I found some explanations later, in the another Generics page.

[BobDog]

This is still a simple one, but I had a try for practise.

Code: Pascal  [Select][+][-]

1.  
2. {$mode delphi}
3.  
4. type udt<T>=class
5. private
6. procedure switch(var a, b: T);
7. public
8. arr:array of T;
9. procedure bubblesort(n:int32);
10. procedure print();
11. procedure setup(n:int32);
12. end;
13.  
14. procedure udt<T>.setup(n:int32);
15. begin
16.   setlength(arr,n);
17. end;
18.  
19. procedure udt<T>.print();
20. var i:int32;
21. begin
22. for i:=0 to high(arr) do write(arr[i],' ');
23. writeln;
24. end;
25.  
26. procedure udt<T>.switch(var a, b: T);
27. var temp: T;
28. begin
29.   temp := a; a := b; b := temp;
30. end;
31.  
32. procedure udt<T>.bubblesort(n:int32);
33. var
34. i:int32;
35. begin
36. if (n = 1) then exit;
37.     for i:=0 to n-2 do if (arr[i] > arr[i+1]) then switch(arr[i],arr[i+1]);
38.     bubbleSort(n-1);
39. end;
40.  
41. var
42. u:udt<integer>;
43. v:udt<string>;
44. i:int32;
45.  
46. begin
47. u:=udt<integer>.create;
48. u.setup(35);
49. for i:=0 to high(u.arr) do u.arr[i]:=random(100);
50. u.print;
51. u.bubblesort(length(u.arr));
52. u.print;
53. writeln;
54. //=========================//
55. v:=udt<string>.create;
56. v.setup(50);
57. for i:=0 to high(v.arr) do v.arr[i]:=chr(65+random(90-64));
58. v.print;
59. v.bubblesort(length(v.arr));
60. v.print;
61. writeln('Press return to end . . .');
62. readln;
63. end.
64.  
65.