promote_scalar.hpp

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#ifndef STAN__MATH__FUNCTIONS__PROMOTE_SCALAR_HPP
#define STAN__MATH__FUNCTIONS__PROMOTE_SCALAR_HPP

#include <vector>
#include <stan/math/functions/promote_scalar_type.hpp>
#include <stan/math/meta/index_type.hpp>

namespace stan {

  namespace math {

    template <typename T, typename S>
    struct promote_scalar_struct {

      static T apply(S x) {
        return T(x);
      }
    };

    template <typename T>
    struct promote_scalar_struct<T,T> {

      static T apply(const T& x) {
        return x;
      }
    };

    template <typename T, typename S>
    struct promote_scalar_struct<T, std::vector<S> > {

      static std::vector<typename promote_scalar_type<T,S>::type>
      apply(const std::vector<S>& x) {
        typedef std::vector<typename promote_scalar_type<T,S>::type> return_t; 
        typedef typename index_type<return_t>::type idx_t;
        return_t y(x.size());
        for (idx_t i = 0; i < x.size(); ++i)
          y[i] = promote_scalar_struct<T,S>::apply(x[i]);
        return y;
      }

    };

    template <typename T, typename S>
    typename promote_scalar_type<T,S>::type
    promote_scalar(const S& x) {
      return promote_scalar_struct<T,S>::apply(x);
    }


  }
}

#endif