A 
cauchy_distribution random number distribution
produces random numbers 
x
distributed according to
the probability density function
p(x|a,b)=(πb(1+(x−ab)2))−1 .
template<class RealType = double>
  class cauchy_distribution {
  public:
        using result_type = RealType;
    using param_type  = unspecified;
        cauchy_distribution() : cauchy_distribution(0.0) {}
    explicit cauchy_distribution(RealType a, RealType b = 1.0);
    explicit cauchy_distribution(const param_type& parm);
    void reset();
        template<class URBG>
      result_type operator()(URBG& g);
    template<class URBG>
      result_type operator()(URBG& g, const param_type& parm);
        RealType a() const;
    RealType b() const;
    param_type param() const;
    void param(const param_type& parm);
    result_type min() const;
    result_type max() const;
  };