log_inv_logit.hpp

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#ifndef __STAN__MATH__FUNCTIONS__LOG_INV_LOGIT_HPP__
#define __STAN__MATH__FUNCTIONS__LOG_INV_LOGIT_HPP__

#include <boost/math/tools/promotion.hpp>

namespace stan {
  namespace math {

    template <typename T>
    inline typename boost::math::tools::promote_args<T>::type
    log_inv_logit(const T& u) {
      using std::exp;
      if (u < 0.0)
        return u - log1p(exp(u));  // prevent underflow
      return -log1p(exp(-u));
    }

  }
}

#endif