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#pragma once
#include <vector>
using std::vector;
typedef int (*weight_func)(int val);
/*
* It is assumed that start <= val < end are tight bounds, i.e.,
* that start and end-1 have positive weights. This could be
* changed if a reason turns up.
*/
class random_var
{
int start, end; // can take values with start <= val < end
vector<int> weights;
int total; // sum of weights
public:
explicit random_var(int c);
random_var(int s, int e, weight_func w_ = nullptr);
random_var(int s, int e, vector<int> ws);
random_var(const random_var &) = default;
random_var(random_var &&) = default;
random_var& operator=(const random_var&) = default;
random_var& operator=(random_var&&) = default;
int weight(int val) const;
int roll() const; // evaluate the random variable
double expected() const; // expected value
int min() const;
int max() const;
protected:
void init_weights(weight_func w);
void reduce_weights();
void init();
int roll2val(int r) const;
bool weights_divisible_by(int factor) const;
};
random_var operator+(const random_var& x, const random_var& y);
random_var negate(const random_var& x);
random_var operator-(const random_var& x, const random_var& y);
const random_var& operator+=(random_var& x, const random_var& y);
const random_var& operator-=(random_var& x, const random_var& y);
random_var operator/(const random_var& x, int d);
random_var operator*(const random_var& x, int d);
random_var div_rand_round(const random_var& x, int d);
namespace rv
{
random_var max(const random_var& x, const random_var& y);
random_var min(const random_var& x, const random_var& y);
random_var roll_dice(int d, int n);
random_var random2(int n);
}
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