std::exponential_distribution::exponential_distribution
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                    < cpp | numeric | random | exponential distribution
                    
                                                            
                    | explicit exponential_distribution( RealType lambda = 1.0 ); | (1) | (since C++11) | 
| explicit exponential_distribution( const param_type& params ); | (2) | (since C++11) | 
Constructs a new distribution object. The first version uses lambda as the distribution parameter, the second version uses params as the distribution parameter.
Parameters
| lambda | - | the λ distribution parameter (the rate parameter) | 
| params | - | the distribution parameter set | 
Notes
Requires that 0 < lambda.