Feature announcement: Function References and Anonymous Functions

[deadserious]

Eventually it will be released as 3.4.0, but the exact schedule for that is still unknown.

Is there a roadmap of fixes/features we're waiting on for 3.4?

Perhaps this will help:

https://wiki.freepascal.org/FPC_New_Features_Trunk

Revision history shows last change in June 2023.

This looks like a list of new features done waiting for 3.4 release to be included?

I'm looking for a list of things that need to be completed before the 3.4 release can be finished.

[PascalDragon]

I'm looking for a list of things that need to be completed before the 3.4 release can be finished.

There is none. We'll start release preparation for 3.4.0 when we think we've reached a suitable point. This is currently not in sight and even then release preparation takes multiple months.

[Okoba]

Hello,

This code in mode Delphi crashes, is it a bug? No problem on objfpc mode.
Tested on today Trunk.

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3.   {$mode Delphi}
4.   {$modeswitch functionreferences}
5.  
6. type
7.   TTest = reference to procedure(V: Integer);
8.  
9.   procedure Test1(V: Integer);
10.   begin
11.     WriteLn('Test1: ', V);
12.   end;
13.  
14.   procedure Run;
15.  
16.     procedure Test2(V: Integer);
17.     begin
18.       WriteLn('Test2: ', V);
19.     end;
20.  
21.   var
22.     T: TTest;
23.   begin
24.     T := @Test2; //Error on Delphi mode but not objfpc
25.     T(1);
26.   end;
27.  
28. begin
29.   Run;
30.   ReadLn;
31. end.                                  

[Paolo]

What about removing "@" ?

[Okoba]

That fixes the problem.
But why? As I remember even in Delphi mode, we use @ to address a function.
Is there a mode switch to activate using @ in Delphi mode?

[dseligo]

That fixes the problem.
But why? As I remember even in Delphi mode, we use @ to address a function.
Is there a mode switch to activate using @ in Delphi mode?

You use @ to get address, but not to assign procedure or function.
See here (first one): https://www.freepascal.org/docs-html/prog/progse74.html

[Okoba]

So why compilers does not throw any error? If @ in Delphi mode is not accepted? It throws an error if I want to set a pointer of an integer to another one.

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3. var
4.   I, J: Integer;
5. begin
6.   I := @J;
7. end.        

And on checking again without 'reference to' the variable, it is zero instead of the correct one, raising the question of why this time it accepts the procedure and even runs it, but with the wrong parameters?

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3.   {$mode Delphi}
4.  
5. type
6.   TTest = procedure(V: Integer);
7.  
8.   procedure Test1(V: Integer);
9.   begin
10.     WriteLn('Test1: ', V);
11.   end;
12.  
13.   procedure Run;
14.  
15.     procedure Test2(V: Integer);
16.     begin
17.       WriteLn('Test2: ', V);
18.     end;
19.  
20.   var
21.     T: TTest;
22.   begin
23.     T := @Test2;
24.     T(1); //Writes 0
25.   end;
26.  
27. begin
28.   Run;
29.   ReadLn;
30. end.

[Paolo]

I tested this code

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. //{$mode delphi}{$H+}
4. {$mode objfpc}{$H+}
5.  
6. interface
7.  
8. uses
9.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, StdCtrls;
10.  
11. type
12.  
13.   { TForm1 }
14.  
15.   TForm1 = class(TForm)
16.     Button1: TButton;
17.     procedure Button1Click(Sender: TObject);
18.   private
19.  
20.   public
21.  
22.   end;
23.  
24. var
25.   Form1: TForm1;
26.  
27. implementation
28.  
29. {$R *.lfm}
30. type
31.  
32.   TTest = procedure(V: Integer);
33.  
34.   procedure Test2(V: Integer);
35.   begin
36.     form1.caption:='Test2: '+V.tostring;
37.   end;
38.  
39.   { TForm1 }
40.  
41.   procedure TForm1.Button1Click(Sender: TObject);
42.   var
43.     T: TTest;
44.   begin
45.     T := Test2;
46.     T(3); //Writes 3
47.   end;
48.  
49. end.
50.  

it always works, just in objfpc mode without @ does not compile

[PascalDragon]

So why compilers does not throw any error? If @ in Delphi mode is not accepted?

Because nobody said that the compiler is flawless. And the function reference functionality is a complicated one... 🙄
Please report a bug.

[Okoba]

Reported: 40626
@PascalDragon except this issue, I should say, Function reference works very well and easy, thank you!

[deadserious]

We'll start release preparation for 3.4.0 when we think we've reached a suitable point.

What makes for a "suitable point"?

[Thaddy]

'when it is ready', as usual. release management is a lot of work.
- documentation ready
- test suites run without error
- new features completed or decided to postpone
- regressions fixed
- new platforms done
- packaging for all platforms done
- release notes written
and possibly more

[beria2]

'when it is ready', as usual. release management is a lot of work.
- documentation ready
- test suites run without error
- new features completed or decided to postpone
- regressions fixed
- new platforms done
- packaging for all platforms done
- release notes written
and possibly more

when will support for anonymous functions be added to objfpc? I'm tired of waiting because I don't see anything difficult about it.  :'( :'( :'( :'( :'( :'( :'(

[TRon]

when will support for anonymous functions be added to objfpc? I'm tired of waiting because I don't see anything difficult about it.  :'( :'( :'( :'( :'( :'( :'(

Did you even read the announcement ? Available since may 2022 in trunk so no idea what you're waiting for tbh.

[beria2]

when will support for anonymous functions be added to objfpc? I'm tired of waiting because I don't see anything difficult about it.  :'( :'( :'( :'( :'( :'( :'(

Did you even read the announcement ? Available since may 2022 in trunk so no idea what you're waiting for tbh.

Free Pascal Compiler version 3.3.1-17783-gf672d4cccf-dirty [2025/04/10] for x86_64
-----------------------------
{$mode objfpc}
begin

    procedure(const aArg: String)
  begin
    Writeln(aArg);
  end('Hello World');

number.lpr(897,5) Error: Illegal expression

---------------
    {$MODE DELPHI}
       

begin

    procedure(const aArg: String)
  begin
    Writeln(aArg);
  end('Hello World');

Ok!
-------------------------------------
I still can't use them.... I'm probably very stupid and I don't understand something in principle. There are a lot of things in fpc that are unclear, which work, which don't, and so they work...