1 #ifndef STAN_MATH_REV_CORE_STD_ISNAN_HPP
2 #define STAN_MATH_REV_CORE_STD_ISNAN_HPP
3 
4 #include <stan/math/rev/core/var.hpp>
5 #include <cmath>
6 
7 namespace std {
8 
9 /**
10  * Checks if the given number is NaN.
11  *
12  * Return <code>true</code> if the value of the
13  * specified variable is not a number.
14  *
15  * @param a Variable to test.
16  * @return <code>true</code> if value is not a number.
17  */
isnan(const stan::math::var & a)18 inline bool isnan(const stan::math::var& a) { return isnan(a.val()); }
19 
20 }  // namespace std
21 #endif
22