[Development] RFC: lambda or lambda return from lambda?

[André Somers]

Op 01/02/2016 om 15:16 schreef Marc Mutz:
> On Monday 01 February 2016 10:18:25 Jędrzej Nowacki wrote:
>> So it would look like that:
>>
>>    fields.erase(std::remove_if(fields.begin(),
>>                                fields.end(),
>>                                [&name](const QPair<QByteArray, QByteArray>
>> &header)
>>                                    {
>>                                        return qstricmp(name.constData(),
>> header.first) == 0;
>>                                    }),
>>                 fields.end());
>>
>> // I hope that formating is still ok, and the code is not wrapped.
>>
> I am a great fanboy of algorithms and the STL, as should be clear by now :)
>
> But I find the inlined lambda worse than an explicit loop. This is write-only
> code, imo. Esp. since we can't (yet) use auto in the parameter list, but even
> then, I'd always give a lambda a name (cf. my mail in response to Christian).
While I applaud the naming of things, especiallly things non-trivial, I 
don't agree that an inlined lambda equates to write-only code. It can 
be, but doesn't need to be. The lambda-to-return a lambda looks more 
write-only than an inlined lambda does, IMHO.

While self-documenting code is great, I don't think it should come at 
the price of outlandish constructs like lambdas-returning-lambdas. It 
cleans up the code at the place you call the code, I give you that, but 
it makes the lambda definition itself too complicated. I prefer a 
comment if you think that documenting what is captured at the call site 
is needed.

  auto firstEqualsName = [&name](const QPair<QByteArray, QByteArray> &header)
  {
       return qstricmp(name.constData(), header.first) == 0;
  };
  fields.erase(std::remove_if(fields.begin(), fields.end(),
                              firstEqualsName /*captures &name*/),
               fields.end());


Though for this particular construct, I certainly prefer a special 
function. The erase + remove_if, both using the same end iterator always 
annoys me.  So something like:

removeWhereFirstEquals(container c, const QByteArray& name);

André