constants.h

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#ifndef FCL_MATH_CONSTANTS_
#define FCL_MATH_CONSTANTS_

#include "fcl/common/types.h"

#include <limits>
#include <cmath>

namespace fcl {

namespace detail {

// Helper struct for determining the underlying numerical type of scalars.
// Allows us to treat AutoDiffScalar<double> and double as double type and
// AutoDiffScalar<float> and float as float type.
template<typename S>
struct ScalarTrait {
  // NOTE: This relies on AutoDiffScalar's `Real` class member and serves as
  // an entry path for any custom scalar class that likewise defines a `Real`
  // class member.
  typedef typename S::Real type;
};

template<>
struct ScalarTrait<long double> {
  typedef long double type;
};

template<>
struct ScalarTrait<double> {
  typedef double type;
};

template<>
struct ScalarTrait<float> {
  typedef float type;
};

}  // namespace detail

template <typename S>
struct FCL_EXPORT constants
{
typedef typename detail::ScalarTrait<S>::type Real;

static constexpr S pi() { return S(3.141592653589793238462643383279502884197169399375105820974944592L); }

static constexpr S phi() { return S(1.618033988749894848204586834365638117720309179805762862135448623L); }

static Real gjk_default_tolerance() {
  static const Real value = eps_78();
  return value;
}

static constexpr Real eps() {
  static_assert(std::is_floating_point<Real>::value,
                "Constants can only be evaluated for scalars with floating "
                "point implementations");
  return std::numeric_limits<Real>::epsilon();
}

// TODO(SeanCurtis-TRI) These are *not* declared constexpr because the clang
//  compiler available in the current CI configuration for ubuntu and mac does
//  not have std::pow declared as constexpr. When that changes, these can
//  likewise be declared as constexpr.

static Real eps_78() {
  static const Real value = std::pow(eps(), 7./8.);
  return value;
}

static Real eps_34() {
  static const Real value = std::pow(eps(), 3./4.);
  return value;
}

static Real eps_12() {
  static const Real value = std::pow(eps(), 1./2.);
  return value;
}

};

using constantsf = constants<float>;
using constantsd = constants<double>;

} // namespace fcl

#endif