fmax.hpp

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#ifndef STAN_MATH_REV_FUN_FMAX_HPP
#define STAN_MATH_REV_FUN_FMAX_HPP
 
#include <stan/math/rev/meta.hpp>
#include <stan/math/rev/core.hpp>
#include <stan/math/rev/fun/is_nan.hpp>
#include <stan/math/prim/fun/is_nan.hpp>
#include <stan/math/prim/fun/constants.hpp>
 
namespace stan {
namespace math {
 
inline var fmax(const var& a, const var& b) {
  if (unlikely(is_nan(a))) {
    if (unlikely(is_nan(b))) {
      return make_callback_var(NOT_A_NUMBER, [a, b](auto& vi) mutable {
        a.adj() = NOT_A_NUMBER;
        b.adj() = NOT_A_NUMBER;
      });
    }
    return b;
  }
  if (unlikely(is_nan(b))) {
    return a;
  }
  return a > b ? a : b;
}
 
inline var fmax(const var& a, double b) {
  if (unlikely(is_nan(a))) {
    if (unlikely(is_nan(b))) {
      return make_callback_var(
          NOT_A_NUMBER, [a](auto& vi) mutable { a.adj() = NOT_A_NUMBER; });
    }
    return var(b);
  }
  if (unlikely(is_nan(b))) {
    return a;
  }
  return a >= b ? a : var(b);
}
 
inline var fmax(double a, const var& b) {
  if (unlikely(is_nan(b))) {
    if (unlikely(is_nan(a))) {
      return make_callback_var(
          NOT_A_NUMBER, [b](auto& vi) mutable { b.adj() = NOT_A_NUMBER; });
    }
    return var(a);
  }
  if (unlikely(is_nan(a))) {
    return b;
  }
  return a > b ? var(a) : b;
}
 
}  // namespace math
}  // namespace stan
#endif