Re: [eigen] FFT update

[Hauke Heibel <hauke.heibel@xxxxxxxxxxxxxx>]

Hi Benoit,

what I just did recently is this:

template<typename Derived> struct rotate_retval
 : public ReturnByValue<rotate_retval<Derived> >
{
  rotate_retval(const DenseBase<Derived>& src) : m_src(src) {}
private:
  const DenseBase<Derived>& m_src;
}

So, I am not storing Derived but a reference to DenseBase<Derived>
(might be ArrayBase<Derived> or MatrixBase<Derived>, depending on the
application).

Another thing which is really important (just telling it, since I did
it wrong and also lost like 30 minutes). Never return a ReturnByValue
object, but something being derived from it. Otherwise, you derived
class with all the data gets sliced away when just the base class is
copied - that was a really stupid idea of mine.

Finally, evalTo(Dest&) does not necessarily require a .resize() - if I
am not totally mistaken, this is already taken care of by the caller.

Regards,
Hauke

On Sat, Jan 23, 2010 at 7:29 AM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
> By the way, this "ReturnByValue::coeff() crashes by infinite
> recursion" thing is really ugly, I wonder how to fix it!!
>
> C++0x at last brings the ability to remove a base class function from
> a derived class... I wonder how to implement that idea in C++98. Is
> that enable_if?
>
> Benoit
>
> 2010/1/23 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
>> Hi,
>>
>> Here's an example: see attached file.
>> Enjoy!!
>> Benoit
>>
>> 2010/1/22 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
>>> ok let me write an example...
>>>
>>> 2010/1/22 Jitse Niesen <jitse@xxxxxxxxxxxxxxxxx>:
>>>> On Fri, 22 Jan 2010, Benoit Jacob wrote:
>>>>
>>>>> Our "policy" is now:
>>>>> - try to return by value, optimizing with the ReturnByValue class,
>>>>> wherever possible;
>>>>> - otherwise you can just use references.
>>>>
>>>> Can somebody please explain how to use the ReturnByValue class?
>>>> Or should I just extrapolate from the source code?
>>>> I could not find any documentation.
>>>>
>>>> Jitse
>>>>
>>>>
>>>>
>>>
>>
>
>
>