Re: [fpc-pascal] Callbacks as nested functions

2017-10-28 Thread Adriaan van Os 

Ryan Joseph wrote:



On Oct 23, 2017, at 9:05 PM, Michael Van Canneyt  wrote:

It is not the default because neither Delphi nor TP allow this.


then that begs the question, why not? :) If local functions are a useful 
feature then local callbacks should be too.


Because
1. it takes a few extra processor cycles
2. it breaks binary compatibilty.

For a detailed discussion, see 

Regards,

Adriaan van Os
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Re: [fpc-pascal] Callbacks as nested functions

2017-10-23 Thread LacaK 
Btw there is long-time open ...  may be related bug 
https://bugs.freepascal.org/view.php?id=18702


L.


Dňa 23.10.2017 o 16:42 Michael Van Canneyt napísal(a):



On Mon, 23 Oct 2017, Ryan Joseph wrote:




On Oct 23, 2017, at 9:05 PM, Michael Van Canneyt 
 wrote:


It is not the default because neither Delphi nor TP allow this.


then that begs the question, why not? :) If local functions are a 
useful feature then local callbacks should be too.


Well, we're not Delphi compiler developers, TP is long defunct, so 
this is the wrong place to ask :)


Michael.
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Re: [fpc-pascal] Callbacks as nested functions

2017-10-23 Thread Michael Van Canneyt 



On Mon, 23 Oct 2017, Ryan Joseph wrote:





On Oct 23, 2017, at 9:05 PM, Michael Van Canneyt  wrote:

It is not the default because neither Delphi nor TP allow this.


then that begs the question, why not? :) If local functions are a useful 
feature then local callbacks should be too.


Well, we're not Delphi compiler developers, TP is long defunct, 
so this is the wrong place to ask :)


Michael.
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Re: [fpc-pascal] Callbacks as nested functions

2017-10-23 Thread Ryan Joseph 


> On Oct 23, 2017, at 9:05 PM, Michael Van Canneyt  
> wrote:
> 
> It is not the default because neither Delphi nor TP allow this.

then that begs the question, why not? :) If local functions are a useful 
feature then local callbacks should be too.

Regards,
Ryan Joseph

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Re: [fpc-pascal] Callbacks as nested functions

2017-10-23 Thread Michael Van Canneyt 



On Mon, 23 Oct 2017, Ryan Joseph wrote:





On Oct 23, 2017, at 8:55 PM, Mattias Gaertner  wrote:

program test1;

{$mode objfpc}{$H+}
{$ModeSwitch nestedprocvars}

type
 TCallback = procedure (a: integer) is nested;

procedure DoCallback;
 procedure DoThis(a: integer);
 begin
   writeln(a);
 end;
var
 callback: TCallback;
begin
 callback := @DoThis;
 callback(100);
end;

begin
 DoCallback;
end.

Keep in mind what Sven wrote. You cannot use "callback" outside of
DoCallBack, because FPC does not yet support Delphi's "reference to".


Thanks, I never heard of nestedprocvars. Why isn’t that the default? If I have 
a callback I may have it be nested or not so I always want “is nested” on I 
guess.


It is not the default because neither Delphi nor TP allow this.

Macpas mode enables it, since it was allowed in MWP.

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Re: [fpc-pascal] Callbacks as nested functions

2017-10-23 Thread Ryan Joseph 


> On Oct 23, 2017, at 8:55 PM, Mattias Gaertner  
> wrote:
> 
> program test1;
> 
> {$mode objfpc}{$H+}
> {$ModeSwitch nestedprocvars}
> 
> type
>  TCallback = procedure (a: integer) is nested;
> 
> procedure DoCallback;
>  procedure DoThis(a: integer);
>  begin
>writeln(a);
>  end;
> var
>  callback: TCallback;
> begin
>  callback := @DoThis;
>  callback(100);
> end;
> 
> begin
>  DoCallback;
> end.
> 
> Keep in mind what Sven wrote. You cannot use "callback" outside of
> DoCallBack, because FPC does not yet support Delphi's "reference to".

Thanks, I never heard of nestedprocvars. Why isn’t that the default? If I have 
a callback I may have it be nested or not so I always want “is nested” on I 
guess.

Regards,
Ryan Joseph

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Re: [fpc-pascal] Callbacks as nested functions

2017-10-23 Thread Mattias Gaertner 
On Mon, 23 Oct 2017 20:04:36 +0700
Ryan Joseph  wrote:

> > On Oct 23, 2017, at 4:56 PM, Sven Barth via fpc-pascal 
> >  wrote:
> > 
> > What exactly are you trying? If the nested function accesses its outer 
> > scope then it definitely won't work. For that you'd need to wait for 
> > anonymous function support (which are planned - at least a far as I'm 
> > concerned - to also support nested functions). 
> >   
> 
> I cast DoThis to the type but the arguments are not correct not and a does 
> not equal 0.

program test1;

{$mode objfpc}{$H+}
{$ModeSwitch nestedprocvars}

type
  TCallback = procedure (a: integer) is nested;

procedure DoCallback;
  procedure DoThis(a: integer);
  begin
writeln(a);
  end;
var
  callback: TCallback;
begin
  callback := @DoThis;
  callback(100);
end;

begin
  DoCallback;
end.

Keep in mind what Sven wrote. You cannot use "callback" outside of
DoCallBack, because FPC does not yet support Delphi's "reference to".

Mattias
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Re: [fpc-pascal] Callbacks as nested functions

2017-10-23 Thread Michael Van Canneyt 



On Mon, 23 Oct 2017, Ryan Joseph wrote:





On Oct 23, 2017, at 4:56 PM, Sven Barth via fpc-pascal 
 wrote:

What exactly are you trying? If the nested function accesses its outer scope then it definitely won't work. For that you'd need to wait for anonymous function support (which are planned - at least a far as I'm concerned - to also support nested functions). 



I cast DoThis to the type but the arguments are not correct not and a does not 
equal 0.

type
TCallback = procedure (a: integer);

procedure DoCallback;
procedure DoThis(a: integer);
begin
writeln(a);
end;
var
callback: TCallback;
begin
callback := TCallback(@DoThis);
callback(100);
end;


You can't use a local procedure for this, as far as I know.

Michael.
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Re: [fpc-pascal] Callbacks as nested functions

2017-10-23 Thread Ryan Joseph 


> On Oct 23, 2017, at 4:56 PM, Sven Barth via fpc-pascal 
>  wrote:
> 
> What exactly are you trying? If the nested function accesses its outer scope 
> then it definitely won't work. For that you'd need to wait for anonymous 
> function support (which are planned - at least a far as I'm concerned - to 
> also support nested functions). 
> 

I cast DoThis to the type but the arguments are not correct not and a does not 
equal 0.

type
TCallback = procedure (a: integer);

procedure DoCallback;
procedure DoThis(a: integer);
begin
writeln(a);
end;
var
callback: TCallback;
begin
callback := TCallback(@DoThis);
callback(100);
end;


Regards,
Ryan Joseph

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Re: [fpc-pascal] Callbacks as nested functions

2017-10-23 Thread Sven Barth via fpc-pascal 
Am 23.10.2017 11:49 schrieb "Ryan Joseph" :

Is there anyway to get callbacks to work as nested functions? I get crashes
when I try this and I assume it’s because the the compiler is replacing the
first parameter with another value.


What exactly are you trying? If the nested function accesses its outer
scope then it definitely won't work. For that you'd need to wait for
anonymous function support (which are planned - at least a far as I'm
concerned - to also support nested functions).

Regards,
Sven
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[fpc-pascal] Callbacks as nested functions

2017-10-23 Thread Ryan Joseph 
Is there anyway to get callbacks to work as nested functions? I get crashes 
when I try this and I assume it’s because the the compiler is replacing the 
first parameter with another value.

Regards,
Ryan Joseph

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