using reng = default_random_engine; // type of engine
using dist = uniform_int_distribution<>; // type of distribution
reng re {}; // the default engine
dist one_to_six {1,6}; // distribution that maps to the ints 1..6
auto die = bind(one_to_six, re); // make a generator
int x = die(); // roll the die: x becomes a value in [1:6]
The standard-library function bind() makes a function object that will invoke its first argument (here, one_to_six) given its second argument (here, re) as its argument (§11.5.1). Thus a call die() is equivalent to a call one_to_six(re).
auto die = bind(uniform_int_distribution<>{1,6}, default_random_engine{});
class Rand_int {
public:
Rand_int(int low, int high) :dist{low,high} { }
int operator()() { return dist(re); } // draw an int
private:
default_random_engine re;
uniform_int_distribution<> dist;
};
int main()
{
constexpr int max = 8; // make a uniform random number generator
Rand_int rnd {0, max};
vector<int> histogram(max+1); // make a vector of appropriate size
for (int i = 0; i != 200; ++i)
++histogram[rnd()]; // fill histogram with the frequencies of numbers [0:max]
for (int i = 0; i != histogram.size(); ++i) { // writes out a bar graph
cout << i << '\t';
for (int j=0; j != histogram[i]; ++j) cout << '*';
cout << endl;
}
}
Output
0 *********************
1 ****************
2 *******************
3 ********************
4 ****************
5 ***********************
6 **************************
7 ***********
8 **********************
9 *************************
