text: #ifndef STAN_MATH_PRIM_SCAL_FUN_TGAMMA_HPP
  #define STAN_MATH_PRIM_SCAL_FUN_TGAMMA_HPP
  
  #include <boost/math/special_functions/gamma.hpp>
  
  namespace stan {
    namespace math {
  
      /**
       * Return the gamma function applied to the specified argument.
       *
       * @param x Argument.
       * @return The gamma function applied to argument.
       */
      inline double tgamma(double x) {
        return boost::math::tgamma(x);
      }
  
    }
  }
  #endif
  