log1m.hpp

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#ifndef __STAN__AGRAD__REV__LOG1M_HPP__
#define __STAN__AGRAD__REV__LOG1M_HPP__

#include <valarray>
#include <stan/agrad/rev/var.hpp>
#include <stan/agrad/rev/op/v_vari.hpp>
#include <stan/math/constants.hpp>
#include <stan/math/functions/log1p.hpp>

namespace stan {
  namespace agrad {

    namespace {
      class log1m_vari : public op_v_vari {
      public:
        log1m_vari(vari* avi) :
          op_v_vari(stan::math::log1p(-avi->val_),avi) {
        }
        void chain() {
          avi_->adj_ += adj_ / (avi_->val_ - 1);
        }
      };
    }

    inline var log1m(const stan::agrad::var& a) {
      return var(new log1m_vari(a.vi_));
    }

  }
}
#endif