#ifndef STAN_MATH_PRIM_MAT_FUN_TRACE_QUAD_FORM_HPP
#define STAN_MATH_PRIM_MAT_FUN_TRACE_QUAD_FORM_HPP

#include <stan/math/prim/mat/fun/Eigen.hpp>
#include <stan/math/prim/mat/err/check_multiplicable.hpp>
#include <stan/math/prim/mat/err/check_square.hpp>

namespace stan {
  namespace math {
    /**
     * Compute trace(B^T A B).
     **/
    template<int RA, int CA, int RB, int CB>
    inline double
    trace_quad_form(const Eigen::Matrix<double, RA, CA> &A,
                    const Eigen::Matrix<double, RB, CB> &B) {
      check_square("trace_quad_form", "A", A);
      check_multiplicable("trace_quad_form",
                          "A", A,
                          "B", B);

      return (B.transpose()*A*B).trace();
    }

  }
}
#endif
