[fpc-devel] Delphi anonymous methods

[Mattias Gaertner]

On Mon, 04 Mar 2013 11:17:53 +0000
Martin <lazarus at mfriebe.de> wrote:

> On 04/03/2013 04:54, Boian Mitov wrote:
> > Here is example:
> >
> > Parallel execution with selection of executor:
> >
> > for i := 0 to AMaxScaleIndex - 1 do
> >  begin
> >  APerIterationLocations.Add( TRTDynamicList<TVLImageRect>.Create() );
> >  AExecutionTask.Add( AExecutor.Execute(
> >      procedure()
> >      begin
> >        ProcessOne( levelScale[ i ], img, hitThreshold, winStride, 
> > padding, APerIterationLocations[ i ] );
> >      end
> >    ));
> >
> >  end;
> >
> > In this case, not only you save declaration, you save the need to 
> > write a whole new class just for the task.
> > This code reduced well over 30 lines of code alone.
> > I have a lot of other examples as well ;-) .
> 
> Ok, I can see the closure helping, but why the anonymous procedure?
> 
> If FPC would offer something like this:
> 
> Procedure Foo;
> var
>    // your locals
>       procedure  Bar(); closure;
>         begin
>           ProcessOne( levelScale[ i ], img, hitThreshold, winStride, 
> padding, APerIterationLocations[ i ] );
>         end
> begin
>    // your code from above
>    for i := 0 to AMaxScaleIndex - 1 do
>     begin
>     APerIterationLocations.Add( TRTDynamicList<TVLImageRect>.Create() );
>     AExecutionTask.Add( AExecutor.Execute( @Bar  ));
> end;
> 
> I added:
>   - the name "Bar"
> - Used is at reference
> - the keyword "closure"
> 
> The above code would then create the exact same closure, as your code 
> does. And it does not need an anonymous method.

Nice. Gimme, gimme.

 
Mattias