square.hpp

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#ifndef STAN_MATH_REV_FUN_SQUARE_HPP
#define STAN_MATH_REV_FUN_SQUARE_HPP
 
#include <stan/math/rev/meta.hpp>
#include <stan/math/rev/core.hpp>
 
namespace stan {
namespace math {
 
inline var square(const var& x) {
  return make_callback_var(square(x.val()), [x](auto& vi) mutable {
    x.adj() += vi.adj() * 2.0 * x.val();
  });
}
 
template <typename T, require_var_matrix_t<T>* = nullptr>
inline auto square(const T& x) {
  return make_callback_var(
      (x.val().array().square()).matrix(), [x](const auto& vi) mutable {
        x.adj() += (2.0 * x.val().array() * vi.adj().array()).matrix();
      });
}
 
}  // namespace math
}  // namespace stan
#endif