acos.hpp

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#ifndef STAN_MATH_REV_FUN_ACOS_HPP
#define STAN_MATH_REV_FUN_ACOS_HPP
 
#include <stan/math/prim/fun/acos.hpp>
#include <stan/math/rev/core.hpp>
#include <stan/math/rev/meta.hpp>
#include <stan/math/rev/fun/abs.hpp>
#include <stan/math/rev/fun/arg.hpp>
#include <stan/math/rev/fun/asin.hpp>
#include <stan/math/rev/fun/is_inf.hpp>
#include <stan/math/rev/fun/is_nan.hpp>
#include <stan/math/rev/fun/polar.hpp>
#include <cmath>
#include <complex>
 
namespace stan {
namespace math {
 
inline var acos(const var& x) {
  return make_callback_var(std::acos(x.val()), [x](const auto& vi) mutable {
    x.adj() -= vi.adj() / std::sqrt(1.0 - (x.val() * x.val()));
  });
}
 
template <typename VarMat, require_var_matrix_t<VarMat>* = nullptr>
inline auto acos(const VarMat& x) {
  return make_callback_var(
      x.val().array().acos().matrix(), [x](const auto& vi) mutable {
        x.adj().array()
            -= vi.adj().array() / (1.0 - (x.val().array().square())).sqrt();
      });
}
 
inline std::complex<var> acos(const std::complex<var>& x) {
  return stan::math::internal::complex_acos(x);
}
 
}  // namespace math
}  // namespace stan
#endif