log.hpp

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#ifndef STAN_MATH_FWD_SCAL_FUN_LOG_HPP
#define STAN_MATH_FWD_SCAL_FUN_LOG_HPP

#include <stan/math/fwd/core.hpp>

#include <stan/math/prim/scal/fun/constants.hpp>

namespace stan {
namespace math {

template <typename T>
inline fvar<T> log(const fvar<T>& x) {
  using std::log;
  if (x.val_ < 0.0)
    return fvar<T>(NOT_A_NUMBER, NOT_A_NUMBER);
  else
    return fvar<T>(log(x.val_), x.d_ / x.val_);
}
}  // namespace math
}  // namespace stan
#endif