A gamma_distribution random number distribution produces random numbers x > 0 distributed according to the probability density function p(x | α,β) = e-x/β βα · Γ(α) · x α-1 .
template<class RealType = double>
 class gamma_distribution{
public:
 // types
 typedef RealType result_type;
 typedef unspecified param_type;
 // constructors and reset functions
 explicit gamma_distribution(RealType alpha = 1.0, RealType beta = 1.0);
 explicit gamma_distribution(const param_type& parm);
 void reset();
 // generating functions
 template<class URNG>
   result_type operator()(URNG& g);
 template<class URNG>
   result_type operator()(URNG& g, const param_type& parm);
 // property functions
 RealType alpha() const;
 RealType beta() const;
 param_type param() const;
 void param(const param_type& parm);
 result_type min() const;
 result_type max() const;
};
explicit gamma_distribution(RealType alpha = 1.0, RealType beta = 1.0);
Requires: 0 < alpha and 0 < beta .
Effects: Constructs a gamma_distribution object; alpha and beta correspond to the parameters of the distribution.
Returns: The value of the alpha parameter with which the object was constructed.
Returns: The value of the beta parameter with which the object was constructed.