c-resources/CPlusPlus20ForProgrammers-m.../examples/ch06/histogram.cpp

61 lines
2.4 KiB
C++

// fig06_07.cpp
// Die-rolling program using an array instead of switch.
//#include <format> // C++20: This will be #include <format>
#include <iostream>
#include <array>
#include <random>
template <int N>
void accumulate(std::array<double, N>& histogram, double val, double lower, double upper){
double del {(upper-lower)/N};
for (int i{0}; i < N; i++){
if ( val > i*del && val < (i+1) * del )
histogram[i]++;
}
return;
}
int main() {
// set up random-number generation
std::random_device rd; // used to seed the default_random_engine
std::default_random_engine engine{rd()}; // rd() produces a seed
double upper_bound = 1;
double lower_bound = 0;
std::uniform_real_distribution<double> randomReal{lower_bound, upper_bound};
constexpr size_t N{4};
double del {(upper_bound-lower_bound)/N};
std::array<double, N> histogram{};
// roll die 60,000 times; use die value as frequency index
for (int roll{1}; roll <= 6000; ++roll) {
double val{ randomReal(engine)};
accumulate<N>(histogram, val, lower_bound, upper_bound);
}
std::cout << " Histogram : \n";
// output each array element's value
for (size_t face{1}; face < histogram.size(); ++face) {
std::cout <<"Number of samples between " << lower_bound+face*del << " and " << lower_bound+(face+1)*del << " is " << histogram.at(face) << "\n";
}
}
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