id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
6937	Wrong cdf/pdf/quantile domain checks for some probability distributions	Florian Schoppmann <Florian.Schoppmann@…>	John Maddock	"`students_t_distribution` and `fisher_f_distribution` are affected, and possibly others (have not checked yet).

`quantile(const students_t[...])` contains the following code:
{{{
   if(false == detail::check_df(
      function, degrees_of_freedom, &error_result, Policy())
         && detail::check_probability(function, probability, &error_result, Policy()))
      return error_result;
}}}

`quantile(const fisher_f[...])` contains:
{{{
   if(false == detail::check_df(
            function, df1, &error_result, Policy())
         && detail::check_df(
            function, df2, &error_result, Policy())
         && detail::check_probability(
            function, p, &error_result, Policy()))
      return error_result;
}}}

The code snippets above would only be correct if the ""`&&`"" operator had precedence over ""`==`"". `pdf` and `cdf` contain code of the same form.

Side effects:
- The Student's t `quantile()` can be called with a probability outside of ![0,1] with unexpected results. Example:
{{{
#include <boost/math/distributions/students_t.hpp>
using namespace boost::math;
int main() {
    std::cout << quantile(students_t(1), 2) << std::endl;
}
}}}
The output is: `-1.84467e+19 `
- The Fisher F `quantile()` function, when called with probability NaN and parameters 1 and 1, leads to a failed BOOST_ASSERT. Example:
{{{
#include <boost/math/distributions/fisher_f.hpp>
using namespace boost::math;
int main() {
    quantile(fisher_f(1, 1), std::numeric_limits<double>::quiet_NaN());
}
}}}
"	Bugs	closed	Boost 1.52.0	math	Boost 1.49.0	Problem	fixed		pbristow@…