c-resources/CPlusPlus20ForProgrammers-m.../examples/ch06/fig06_12.cpp

93 lines
3.0 KiB
C++

// fig06_12.cpp
// Compute the product of an array's elements using accumulate.
#include <array>
#include <iostream>
#include <numeric>
template <typename T>
T multiply(T x, T y) {
return x * y;
}
int multiply_int(int x, int y) {
return x * y;
}
double f(double& x){
return x*x;
}
template <typename T, typename F, long unsigned int N>
T integrate (std::array<T, N> x, F f){
T tmp{T(0)};
for (auto s: x){
tmp+= f(s);
}
return tmp;
}
typedef double (*FUNC)(double&);
template <typename T, long unsigned int N>
T integrate2 (std::array<T, N> x, FUNC f){
T tmp{T(0)};
for (auto s: x){
tmp+= f(s);
}
return tmp;
}
int main() {
constexpr std::array integers{1, 2, 3, 4, 5};
std::array floats {1.0, 2.0, 3.0, 4.0, 5.0};
auto multiply_lambda = [](const auto& x, const auto& y) {return x * y; };
auto f_lambda = [](auto& x) {return x*x;};
auto g_lambda = [&integers](auto& x) {
auto tmp{0};
for (int i{0};auto s: x){
tmp += s*integers[i];
}
return tmp;
};
std::cout << "Product of integers: " << std::accumulate( std::begin(integers), std::end(integers), 1, multiply<int>) << "\n";
std::cout << "Product of integers: " << std::accumulate( integers.cbegin(), integers.cend(), 1, multiply<int>) << "\n";
std::cout << "Product of integers with a lambda: " << std::accumulate(std::begin(integers), std::end(integers), 1, multiply_lambda) << "\n";
std::cout << "Product of integers with a lambda: " << std::accumulate(std::begin(floats), std::end(floats), 1, multiply_int) << "\n";
std::cout << "Product of integers with a lambda: " << std::accumulate(std::begin(floats), std::end(floats), 1, multiply_lambda) << "\n";
std::cout << "Integration2 template " << integrate2(floats, f) << "\n";
std::cout << "Integration full template " << integrate(floats, f_lambda) << "\n";
std::cout << "Lambda test " << g_lambda(floats) << "\n";
}
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