log.hpp

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#ifndef STAN__AGRAD__FWD__FUNCTIONS__LOG_HPP
#define STAN__AGRAD__FWD__FUNCTIONS__LOG_HPP

#include <stan/agrad/fwd/fvar.hpp>
#include <stan/meta/traits.hpp>
#include <stan/math/constants.hpp>

namespace stan {

  namespace agrad {

    template <typename T>
    inline
    fvar<T>
    log(const fvar<T>& x) {
      using std::log;
      using stan::math::NOT_A_NUMBER;
      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_);
    }
  }
}
#endif