inv_erfc.hpp

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#ifndef STAN_MATH_REV_FUN_INV_ERFC_HPP
#define STAN_MATH_REV_FUN_INV_ERFC_HPP
 
#include <stan/math/rev/core.hpp>
#include <stan/math/rev/meta.hpp>
#include <stan/math/prim/fun/constants.hpp>
#include <stan/math/prim/fun/inv_erfc.hpp>
#include <stan/math/prim/fun/square.hpp>
#include <stan/math/prim/fun/exp.hpp>
#include <cmath>
 
namespace stan {
namespace math {
 
inline var inv_erfc(const var& a) {
  auto precomp_inv_erfc = inv_erfc(a.val());
  return make_callback_var(
      precomp_inv_erfc, [a, precomp_inv_erfc](auto& vi) mutable {
        a.adj()
            -= vi.adj() * exp(LOG_SQRT_PI - LOG_TWO + square(precomp_inv_erfc));
      });
}
 
template <typename T, require_matrix_t<T>* = nullptr>
inline auto inv_erfc(const var_value<T>& a) {
  auto precomp_inv_erfc = to_arena(inv_erfc(a.val()));
  return make_callback_var(
      precomp_inv_erfc, [a, precomp_inv_erfc](auto& vi) mutable {
        a.adj().array()
            -= vi.adj().array()
               * exp(LOG_SQRT_PI - LOG_TWO + square(precomp_inv_erfc).array());
      });
}
 
}  // namespace math
}  // namespace stan
#endif