Here's the compiler error:
```
/home/tav/git/Sleipnir/build/_deps/eigen3-src/Eigen/src/Householder/Householder.h:82:16: error: call of overloaded ‘sqrt(boost::decimal::decimal64_t)’ is ambiguous
82 | beta = sqrt(numext::abs2(c0) + tailSqNorm);
| ~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/tav/git/Sleipnir/build/_deps/eigen3-src/Eigen/src/Householder/Householder.h:82:16: note: there are 2 candidates
In file included from /home/tav/git/Sleipnir/build/_deps/eigen3-src/Eigen/Core:198,
from /home/tav/git/Sleipnir/test/src/optimization/cart_pole_problem_test.cpp:8:
/home/tav/git/Sleipnir/build/_deps/eigen3-src/Eigen/src/Core/MathFunctions.h:1384:75: note: candidate 1: ‘typename Eigen::internal::sqrt_retval<typename Eigen::internal::global_math_functions_filtering_base<Scalar>::type>::type Eigen::numext::sqrt(const Scalar&) [with Scalar = boost::decimal::decimal64_t; typename Eigen::internal::sqrt_retval<typename Eigen::internal::global_math_functions_filtering_base<Scalar>::type>::type = boost::decimal::decimal64_t; typename Eigen::internal::global_math_functions_filtering_base<Scalar>::type = boost::decimal::decimal64_t]’
1384 | EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE EIGEN_MATHFUNC_RETVAL(sqrt, Scalar) sqrt(const Scalar& x) {
| ^~~~
In file included from /home/tav/git/Sleipnir/build/_deps/decimal-src/include/boost/decimal/detail/cmath/ellint_1.hpp:16,
from /home/tav/git/Sleipnir/build/_deps/decimal-src/include/boost/decimal/cmath.hpp:18,
from /home/tav/git/Sleipnir/build/_deps/decimal-src/include/boost/decimal.hpp:33,
from /home/tav/git/Sleipnir/test/include/scalar_types_under_test.hpp:6,
from /home/tav/git/Sleipnir/test/src/optimization/cart_pole_problem_test.cpp:19:
/home/tav/git/Sleipnir/build/_deps/decimal-src/include/boost/decimal/detail/cmath/sqrt.hpp:167:16: note: candidate 2: ‘constexpr T boost::decimal::sqrt(T) requires is_decimal_floating_point_v<T> [with T = decimal64_t]’
167 | constexpr auto sqrt(const T val) noexcept
| ^~~~
```
Calling a function via its unqualified name invokes argument-dependent lookup. In this case, since `using numext::sqrt;` was used, both `numext::sqrt()` and `boost::decimal::sqrt()` participated in overload resolution. Since only `numext::sqrt()` was intended, the fix is to call that overload directly instead.
See merge request libeigen/eigen!2044
This changeset also includes:
* add HouseholderSequence::conjugateIf
* define int as the StorageIndex type for all dense solvers
* dedicated unit tests, including assertion checking
* _check_solve_assertion(): this method can be implemented in derived solver classes to implement custom checks
* CompleteOrthogonalDecompositions: add applyZOnTheLeftInPlace, fix scalar type in applyZAdjointOnTheLeftInPlace(), add missing assertions
* Cholesky: add missing assertions
* FullPivHouseholderQR: Corrected Scalar type in _solve_impl()
* BDCSVD: Unambiguous return type for ternary operator
* SVDBase: Corrected Scalar type in _solve_impl()
- Replace internal::scalar_product_traits<A,B> by Eigen::ScalarBinaryOpTraits<A,B,OP>
- Remove the "functor_is_product_like" helper (was pretty ugly)
- Currently, OP is not used, but it is available to the user for fine grained tuning
- Currently, only the following operators have been generalized: *,/,+,-,=,*=,/=,+=,-=
- TODO: generalize all other binray operators (comparisons,pow,etc.)
- TODO: handle "scalar op array" operators (currently only * is handled)
- TODO: move the handling of the "void" scalar type to ScalarBinaryOpTraits
