fmod.hpp

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#ifndef STAN__AGRAD__REV__FUNCTIONS__FMOD_HPP
#define STAN__AGRAD__REV__FUNCTIONS__FMOD_HPP

#include <cmath>
#include <stan/agrad/rev/var.hpp>
#include <stan/agrad/rev/internal/vd_vari.hpp>
#include <stan/agrad/rev/internal/vv_vari.hpp>
#include <stan/agrad/rev/internal/dv_vari.hpp>
#include <boost/math/special_functions/fpclassify.hpp>

namespace stan {
  namespace agrad {
    
    namespace {
      class fmod_vv_vari : public op_vv_vari {
      public:
        fmod_vv_vari(vari* avi, vari* bvi) :
          op_vv_vari(std::fmod(avi->val_,bvi->val_),avi,bvi) {
        }
        void chain() {
          if (unlikely(boost::math::isnan(avi_->val_)
                       || boost::math::isnan(bvi_->val_))) {
            avi_->adj_ = std::numeric_limits<double>::quiet_NaN();
            bvi_->adj_ = std::numeric_limits<double>::quiet_NaN();
          } else {
            avi_->adj_ += adj_;
            bvi_->adj_ -= adj_ * static_cast<int>(avi_->val_ / bvi_->val_);
          }
        }
      };

      class fmod_vd_vari : public op_vd_vari {
      public:
        fmod_vd_vari(vari* avi, double b) :
          op_vd_vari(std::fmod(avi->val_,b),avi,b) {
        }
        void chain() {
          if (unlikely(boost::math::isnan(avi_->val_)
                       || boost::math::isnan(bd_)))
            avi_->adj_ = std::numeric_limits<double>::quiet_NaN();
          else
            avi_->adj_ += adj_;
        }
      };
      
      class fmod_dv_vari : public op_dv_vari {
      public:
        fmod_dv_vari(double a, vari* bvi) :
          op_dv_vari(std::fmod(a,bvi->val_),a,bvi) {
        }
        void chain() {
          if (unlikely(boost::math::isnan(bvi_->val_)
                       || boost::math::isnan(ad_)))
            bvi_->adj_ = std::numeric_limits<double>::quiet_NaN();
          else {
            int d = static_cast<int>(ad_ / bvi_->val_);
            bvi_->adj_ -= adj_ * d;
          }
        }
      };
    }
    
    inline var fmod(const var& a, const var& b) {
      return var(new fmod_vv_vari(a.vi_,b.vi_));
    }
  
    inline var fmod(const var& a, const double b) {
      return var(new fmod_vd_vari(a.vi_,b));
    }

    inline var fmod(const double a, const var& b) {
      return var(new fmod_dv_vari(a,b.vi_));
    }

  }
}
#endif