[rand.dist.samp.pconst] (original) (raw)

29 Numerics library [numerics]

29.5 Random number generation [rand]

29.5.9 Random number distribution class templates [rand.dist]

29.5.9.6 Sampling distributions [rand.dist.samp]

29.5.9.6.2 Class template piecewise_constant_distribution [rand.dist.samp.pconst]

A piecewise_constant_distribution random number distribution produces random numbers x,, uniformly distributed over each subintervalaccording to the probability density function in Formula 29.20.

The distribution parameters , also known as this distribution's interval boundaries, shall satisfy the relation for .

Unless specified otherwise, the remaining n distribution parameters are calculated as:
in which the values , commonly known as the weights, shall be non-negative, non-NaN, and non-infinity.

Moreover, the following relation shall hold:.

namespace std { template<class RealType = double> class piecewise_constant_distribution { public: using result_type = RealType;using param_type = unspecified; piecewise_constant_distribution();template<class InputIteratorB, class InputIteratorW> piecewise_constant_distribution(InputIteratorB firstB, InputIteratorB lastB, InputIteratorW firstW);template<class UnaryOperation> piecewise_constant_distribution(initializer_list<RealType> bl, UnaryOperation fw);template<class UnaryOperation> piecewise_constant_distribution(size_t nw, RealType xmin, RealType xmax, UnaryOperation fw);explicit piecewise_constant_distribution(const param_type& parm);void reset();friend bool operator==(const piecewise_constant_distribution& x,const piecewise_constant_distribution& y);template<class URBG> result_type operator()(URBG& g);template<class URBG> result_type operator()(URBG& g, const param_type& parm); vector<result_type> intervals() const; vector<result_type> densities() const; param_type param() const;void param(const param_type& parm); result_type min() const; result_type max() const;template<class charT, class traits> friend basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const piecewise_constant_distribution& x);template<class charT, class traits> friend basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>& is, piecewise_constant_distribution& x);};}

piecewise_constant_distribution();

Effects: Constructs a piecewise_constant_distribution object with ,,, and .

template<class InputIteratorB, class InputIteratorW> piecewise_constant_distribution(InputIteratorB firstB, InputIteratorB lastB, InputIteratorW firstW);

Mandates: Both of

• is_convertible_v<iterator_traits<InputIteratorB>​::​value_type, double>
• is_convertible_v<iterator_traits<InputIteratorW>​::​value_type, double>

are true.

If firstB == lastB or ++firstB == lastB, let ,,, and .

Otherwise,[firstB, lastB) forms a sequence b of length , the length of the sequence w starting from firstW is at least n, and any for k ≥ n are ignored by the distribution.

Effects: Constructs a piecewise_constant_distribution object with parameters as specified above.

template<class UnaryOperation> piecewise_constant_distribution(initializer_list<RealType> bl, UnaryOperation fw);

Mandates: is_invocable_r_v<double, UnaryOperation&, double> is true.

Effects: Constructs a piecewise_constant_distribution object with parameters taken or calculated from the following values: If , let ,,, and .

Otherwise, let [bl.begin(), bl.end()) form a sequence , and let for .

Complexity: The number of invocations of fw does not exceed n.

template<class UnaryOperation> piecewise_constant_distribution(size_t nw, RealType xmin, RealType xmax, UnaryOperation fw);

Mandates: is_invocable_r_v<double, UnaryOperation&, double> is true.

Preconditions: If , let , otherwise let .

The relation holds.

Effects: Constructs a piecewise_constant_distribution object with parameters taken or calculated from the following values: Let for , and for .

Complexity: The number of invocations of fw does not exceed n.

vector<result_type> intervals() const;

Returns: A vector<result_type> whose size member returns and whose operator[] member returns when invoked with argument k for .

vector<result_type> densities() const;

Returns: A vector<result_type> whose size member returns n and whose operator[] member returns when invoked with argument k for .