positive_constrain.hpp

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#ifndef STAN_MATH_PRIM_CONSTRAINT_POSITIVE_CONSTRAIN_HPP
#define STAN_MATH_PRIM_CONSTRAINT_POSITIVE_CONSTRAIN_HPP
 
#include <stan/math/prim/meta.hpp>
#include <stan/math/prim/fun/exp.hpp>
#include <stan/math/prim/fun/sum.hpp>
#include <cmath>
 
namespace stan {
namespace math {
 
template <typename T>
inline auto positive_constrain(const T& x) {
  return exp(x);
}
 
template <typename T, typename S>
inline auto positive_constrain(const T& x, S& lp) {
  lp += sum(x);
  return exp(x);
}
 
template <bool Jacobian, typename T, require_not_std_vector_t<T>* = nullptr>
inline auto positive_constrain(const T& x, return_type_t<T>& lp) {
  if (Jacobian) {
    return positive_constrain(x, lp);
  } else {
    return positive_constrain(x);
  }
}
 
template <bool Jacobian, typename T, require_std_vector_t<T>* = nullptr>
inline auto positive_constrain(const T& x, return_type_t<T>& lp) {
  return apply_vector_unary<T>::apply(
      x, [&lp](auto&& v) { return positive_constrain<Jacobian>(v, lp); });
}
 
}  // namespace math
}  // namespace stan
 
#endif