Re: [eigen] Can we prevent that this compiles?

[Benoit Jacob <jacob.benoit.1@xxxxxxxxx>]

I've just pushed it.

Sorry for wanting "my own, my own!" when your solution was pretty nice already.
I just think that the fewer proxy objects we introduce, the better.
Hope it's OK.

Benoit

2009/10/1 Hauke Heibel <hauke.heibel@xxxxxxxxxxxxxx>:
> Looks good. Shall we apply the patch?
>
> On Wed, Sep 30, 2009 at 9:53 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx>
> wrote:
>>
>> Hi,
>>
>> Thanks for investigating this.
>>
>> I think that we can do simpler while staying with our usual
>> static_assert's which allow better error messages (especially for
>> users who enable the static_assert keyword... just saying that this is
>> the future).
>>
>> The basic problem was that the Replicate constructor was taking an
>> argument of type const MatrixType&, hence by the time it received this
>> argument, it had already been casted to that type, and the information
>> of the original type of that data was lost.
>>
>> So instead, why not make this constructor templated in
>> "OriginalMatrixType" and then do a static assertion that this is the
>> same type as MatrixType.
>>
>> Attached patch.
>>
>> Compiler output (gcc 4.4, default options):
>>
>> $ g++ a.cpp -o a -I eigen2 && ./a
>> In file included from eigen2/Eigen/Array:38,
>>                 from a.cpp:1:
>> eigen2/Eigen/src/Array/Replicate.h: In constructor
>> ‘Eigen::Replicate<MatrixType, RowFactor, ColFactor>::Replicate(const
>> OriginalMatrixType&) [with OriginalMatrixType =
>> Eigen::Block<Eigen::Matrix<double, 33331, 33331, 0, 33331, 33331>, 1,
>> 33331, 1, 32>, MatrixType = Eigen::Matrix<double, 33331, 33331, 0,
>> 33331, 33331>, int RowFactor = 2, int ColFactor = 1]’:
>> a.cpp:8:   instantiated from here
>> eigen2/Eigen/src/Array/Replicate.h:76: error:
>> ‘THE_MATRIX_OR_EXPRESSION_THAT_YOU_PASSED_DOES_NOT_HAVE_THE_EXPECTED_TYPE’
>> is not a member of ‘Eigen::ei_static_assert<false>’
>>
>>
>> of course it looks even much nicer with --std=c++0x:
>>
>> $ g++ a.cpp -o a -I eigen2 --std=c++0x && ./a
>> In file included from eigen2/Eigen/Array:38,
>>                 from a.cpp:1:
>> eigen2/Eigen/src/Array/Replicate.h: In constructor
>> ‘Eigen::Replicate<MatrixType, RowFactor, ColFactor>::Replicate(const
>> OriginalMatrixType&) [with OriginalMatrixType =
>> Eigen::Block<Eigen::Matrix<double, 33331, 33331, 0, 33331, 33331>, 1,
>> 33331, 1, 32>, MatrixType = Eigen::Matrix<double, 33331, 33331, 0,
>> 33331, 33331>, int RowFactor = 2, int ColFactor = 1]’:
>> a.cpp:8:   instantiated from here
>> eigen2/Eigen/src/Array/Replicate.h:76: error: static assertion failed:
>> "THE_MATRIX_OR_EXPRESSION_THAT_YOU_PASSED_DOES_NOT_HAVE_THE_EXPECTED_TYPE"
>>
>> Makes me think that in that case we should make natural strings.
>>
>> Benoit
>>
>>
>>
>>
>>
>> 2009/9/30 Hauke Heibel <hauke.heibel@xxxxxxxxxxxxxx>:
>> > Here, this patch is working. When Gael and/or Benoit agree, I could
>> > submit
>> > it. Though the error message on VC is not very nice...
>> >
>> > Hauke
>> >
>> > ---------- error message - begin ----------
>> > Error    1    error C2664:
>> > 'Eigen::Replicate<MatrixType,RowFactor,ColFactor>::Replicate(const
>> >
>> > Eigen::Replicate<MatrixType,RowFactor,ColFactor>::MustBeInstantiatedWith<MatrixType>
>> > &)' : cannot convert parameter 1 from
>> > 'Eigen::Block<MatrixType,BlockRows,BlockCols>' to 'const
>> >
>> > Eigen::Replicate<MatrixType,RowFactor,ColFactor>::MustBeInstantiatedWith<MatrixType>
>> > &'    main.cpp    9
>> > ---------- error message - end ----------
>> >
>> >
>> > On Wed, Sep 30, 2009 at 5:18 PM, Markus Moll
>> > <markus.moll@xxxxxxxxxxxxxxxx>
>> > wrote:
>> >>
>> >> Hi
>> >>
>> >> On Wednesday 30 September 2009 17:05:28 Hauke Heibel wrote:
>> >> > With static asserts we can make the compile error self explanatory. I
>> >> > preferred the ctor approach since it does not require implementing a
>> >> > ConstRef class.
>> >>
>> >> Hm, but that can be a _very_ thin wrapper even declared inside
>> >> Replicate
>> >> (basically the code I gave is sufficient). It doesn't need to be a
>> >> full-blown
>> >> ConstRef class with all its problems. The more I think about it, the
>> >> less
>> >> I
>> >> like the template solution. Even with static asserts, the error message
>> >> will
>> >> look radically different from what a user might expect. And the type
>> >> ConstRef
>> >> could be named "MustBeInstantiatedFrom" or "ExactType", so that the
>> >> candidate
>> >> list would read:
>> >>
>> >> candidates are:
>> >>  Replicate::Replicate(ExactType<const T&>)
>> >>  Replicate::Replicate(const Replicate&);
>> >>  [... whatever else ...]
>> >>
>> >> Markus
>> >>
>> >> --
>> >> PGP key on www.esat.kuleuven.be/~mmoll/public_key.pgp
>> >> Fingerprint is
>> >> 90C4 B47D 1A00 5AC1 9147  3197 EDA7 1E0E 99E4 9EDB
>> >>
>> >>
>> >
>> >
>
>