[Lazarus] local procedure - MultiThreadProc

[Florian Klaempfl]

Mattias Gärtner schrieb:
> Zitat von Vincent Snijders <vsnijders at vodafonevast.nl>:
> 
>> Martin schreef:
>>> Mattias Gärtner wrote:
>>>> Zitat von Jan Kowalski <bor400 at gmail.com>:
>>>>> I need to call ProcThreadPool.DoParallel with "local" procedure as 
>>>>> a parameter.
>>>>> Does DoParallel allow local procedures to pass a procedural 
>>>>> parameters ?
>>>>> I get err: Error:
>>>>> Incompatible type for arg no. 1: Got "<address of local
>>>>> procedure(Int64,Pointer,TMultiThreadProcItem);Register>", expected
>>>>> "<procedure variable type of
>>>>> procedure(Int64,Pointer,TMultiThreadProcItem);Register>"
>>>>
>>>> That would be really helpful.
>>>> But I don't know how to define a local procedure type:
>>>>
>>> I wouldn't be sure it's possible. It makes no sense.
> 
> It makes enough sense in this case.
> For example when you want to execute a loop in parallel, then you 
> extract the loop into a procedure. With a local procedure you can keep 
> the variables, which would make the process quite easy. If you can not 
> use a local procedure, then you must define a record and move the local 
> variables there.
> Of course nested local procedures creates a whole bunch of problems, so 
> maybe the record approach is much safer.
> Maybe the extract procedure tool can be extended to do some of the 
> monotone work automatically.
> I will explain the process in more detail on the wiki.

You can create a thread call for local procedures, it needs some hacking 
though: no type checking is possible, you've to work with pointers and 
pass the context explicitly.