Generic functions/methods in delphi mode

[XiJinping]

Hello all.

I have a function like:

Code: Pascal  [Select][+][-]

1.   {$ifdef fpc}
2.   {$mode delphi}{$H+}
3.   {$endif fpc}
4.   ...
5.   function SetResultValue<T: class>(Token: TOptValue<T>; Tmp: T): TFail;

but I get "parser.pas(101,28) Fatal: Syntax error, ">" expected but ":" found". I tried also without constraint "class", but then I get "parser.pas(101,47) Error: Identifier not found "T"" and "parser.pas(101,48) Error: Type identifier expected". Also I tried to move this function in a class (initially I need it there). But it leads to errors too. How can I create generic function/method in DELPHI mode?

[Thaddy]

Working example:

Code: Pascal  [Select][+][-]

1. {$ifdef fpc}{$mode delphi}{$H+}{$endif fpc}
2. // the above is a bit dangerous because it won't work in Delphi, only in FPC mode Delphi.
3. // Here's code in Delphi style syntax:
4. uses classes;
5. type
6.   TFail =  type Boolean;
7.   TOptValue<T:class> = record
8.     value:T
9.   end;
10.  
11.   function SetResultValue<T: class>(Token: TOptValue<T>; Tmp: T): TFail;
12.   begin
13.     result := true;
14.     if Token.Value = Tmp then Result := false;
15.   end;
16.  
17. begin
18. end.

Note this code needs FPC 3.2.0 to work and unlike maybe suggested by the mode it DOES NOT WORK in Delphi!!! Delphi doesn't support it.
See: https://wiki.freepascal.org/FPC_New_Features_3.2#Support_for_generic_routines

[XiJinping]

Oh, I got it, I am on FPC 3.0.4. Thank you!

[ASerge]

I am on FPC 3.0.4.

Code: Pascal  [Select][+][-]

1. {$MODE DELPHI}
2.  
3. type
4.   TOptValue<T:class> = record
5.     class function SetResultValue(const Token: TOptValue<T>; const Tmp: T): Boolean; static;
6.   end;
7.  
8. class function TOptValue<T>.SetResultValue(const Token: TOptValue<T>; const Tmp: T): Boolean;
9. begin
10.   Result := True;
11. end;
12.  
13. var
14.   V: TOptValue<TObject> = ();
15. begin
16.   V.SetResultValue(V, nil);
17. end.

[Thaddy]

Nothing wrong with the demo code, since it works both in Delphi and FPC, but: I suppose he knew that and tried the stand-alone feature. That requires 3.2.0.

What is funny is that you should have written something like my {$ifdef} and I should have written something like your {$ifdef} 
Anyway, what about adding both the examples to the wiki, with the proper {$ifdef} 's ?

[PascalDragon]

Note this code needs FPC 3.2.0 to work and unlike maybe suggested by the mode it DOES NOT WORK in Delphi!!! Delphi doesn't support it.
See: https://wiki.freepascal.org/FPC_New_Features_3.2#Support_for_generic_routines

Please note that the idea of the mode concept is that code written for that compiler works in FPC. We do in no way guarantee that the opposite is true (which is why I implemented support for global generic functions also for mode Delphi).