1 #ifndef STAN_MATH_REV_SCAL_FUN_CALCULATE_CHAIN_HPP
2 #define STAN_MATH_REV_SCAL_FUN_CALCULATE_CHAIN_HPP
3 
4 #include <valarray>
5 
6 namespace stan {
7 namespace math {
8 
calculate_chain(double x,double val)9 inline double calculate_chain(double x, double val) {
10   return std::exp(x - val);  // works out to inv_logit(x)
11 }
12 
13 }  // namespace math
14 }  // namespace stan
15 #endif
16