Re: [eigen] unpleasant surprise mit math functions

[Gael Guennebaud <gael.guennebaud@xxxxxxxxx>]

On Thu, Sep 27, 2012 at 12:01 PM, Christoph Hertzberg
<chtz@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> On 27.09.2012 11:28, Hauke Heibel wrote:
>>
>> In summary, I would be glad if it were possible to have the option to
>> call sin/cos and co on Arrays exactly as I can do it in Matlab.
>
>
> I don't think anybody (at least not me) argued for removing
> sin(ArrayBase<...>);
> There are currently two places (see below) where Eigen defines
> Eigen::internal::sin and one where it defines std::sin. I would suggest only
> removing the internal::sin of MathFunctions.h whose purpose only seems to be
> to prevent calling sin(int), however it leads to infinite recursion for
> Matrix-expressions (and maybe actually someone likes to abuse cos(/* int */
> x) for (x==0) *g*)

yes, the plan was only to cleanup the MathFunctions.h file. For the
record, here are two related bug reports:

http://eigen.tuxfamily.org/bz/show_bug.cgi?id=314
http://eigen.tuxfamily.org/bz/show_bug.cgi?id=508

gael

> It might be even wise to define the other Eigen::internal::sin as
> Eigen::sin, that would make both Eigen::sin(array) and sin(array) work.
> I'm not very comfortable with allowing std::sin(array), but I'm ok with that
> for not breaking the API.
> In most applications you would be fine with
> {using std::sin; sin(x); /* x can be scalar or Eigen::ArrayBase<> */ }
>
>
> GlobalFunction.h:
>>
>> namespace std {
>> // Line 42:
>> template<typename Derived> \
>>   inline const Eigen::CwiseUnaryOp<Eigen::internal::scalar_sin_op<typename
>> Derived::Scalar>, const Derived> \
>>   sin(const Eigen::ArrayBase<Derived>& x) { \
>>     return x.derived(); \
>>   }
>> // EOL 42
>> }
>>
>>
>> namespace Eigen { namespace internal {
>> // Line 88:
>> template<typename Derived> \
>>   struct sin_retval<ArrayBase<Derived> > \
>>   { \
>>     typedef const
>> Eigen::CwiseUnaryOp<Eigen::internal::scalar_sin_op<typename
>> Derived::Scalar>, const Derived> type; \
>>   }; \
>>   template<typename Derived> \
>>   struct sin_impl<ArrayBase<Derived> > \
>>   { \
>>     static inline typename sin_retval<ArrayBase<Derived> >::type run(const
>> Eigen::ArrayBase<Derived>& x) \
>>     { \
>>       return x.derived(); \
>>     } \
>>   };
>> // EOL 88
>> }}
>
>
> MathFunctions.h  ONLY REMOVE THESE!
>>
>> namespace Eigen { namespace internal {
>> // Line 476:
>> template<typename Scalar, bool IsInteger> struct sin_default_impl {
>> \
>>     static inline Scalar run(const Scalar& x) { using std::sin; return
>> sin(x); }  \
>>   };
>> \
>>   template<typename Scalar> struct sin_default_impl<Scalar, true> {
>> \
>>     static inline Scalar run(const Scalar&) {
>> \
>>       if
>> (Eigen::internal::static_assertion<bool(!NumTraits<Scalar>::IsInteger)>::THIS_FUNCTION_IS_NOT_FOR_INTEGER_NUMERIC_TYPES)
>> {}                                       \
>>       return Scalar(0);
>> \
>>     }
>> \
>>   };
>> \
>>   template<typename Scalar> struct sin_impl
>> \
>>     : sin_default_impl<Scalar, NumTraits<Scalar>::IsInteger>
>> \
>>   {};
>> \
>>   template<typename Scalar> struct sin_retval { typedef Scalar type; };
>> \
>>   template<typename Scalar>
>> \
>>   inline typename sin_retval<typename
>> global_math_functions_filtering_base<Scalar>::type>::type sin(const Scalar&
>> x) {                \
>>     return sin_impl<typename
>> global_math_functions_filtering_base<Scalar>::type>::run(x);
>> \
>>   }
>> // EOL 476
>> }}
>
>
>
>
> Christoph
>
> --
> ----------------------------------------------
> Dipl.-Inf. Christoph Hertzberg
> Cartesium 0.049
> Universität Bremen
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>
> Tel: +49 (421) 218-64252
> ----------------------------------------------
>
>