c-resources/CPlusPlus20ForProgrammers-m.../examples/ch18/fig18_01.cpp

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// fig18_01.cpp
// Creating a generator coroutine with co_yield.
#include <fmt/format.h>
#include <iostream>
#include <sstream>
#include <thread>
#include <tl/generator.hpp>
// get current thread's ID as a string
std::string id() {
std::ostringstream out;
out << std::this_thread::get_id();
return out.str();
}
// coroutine that repeatedly yields the next Fibonacci value in sequence
tl::generator<int> fibonacciGenerator(int limit) {
std::cout << fmt::format(
"Thread {}: fibonacciGenerator started executing\n", id());
int value1{0}; // Fibonacci(0)
int value2{1}; // Fibonacci(1)
for (int i{0}; i < limit; ++i) {
co_yield value1; // yield current value of value1
// update value1 and value2 for next iteration
int temp{value1 + value2};
value1 = value2;
value2 = temp;
}
std::cout << fmt::format(
"Thread {}: fibonacciGenerator finished executing\n", id());
}
int main() {
std::cout << fmt::format("Thread {}: main begins\n", id());
// display first 10 Fibonacci values
for (int i{0}; auto value : fibonacciGenerator(10)) {
std::cout << fmt::format("Fibonacci({}) is {}\n", i++, value);
}
std::cout << fmt::format("Thread {}: main ends\n", id());
}
/**************************************************************************
* (C) Copyright 1992-2021 by Deitel & Associates, Inc. and *
* Pearson Education, Inc. All Rights Reserved. *
* *
* DISCLAIMER: The authors and publisher of this book have used their *
* best efforts in preparing the book. These efforts include the *
* development, research, and testing of the theories and programs *
* to determine their effectiveness. The authors and publisher make *
* no warranty of any kind, expressed or implied, with regard to these *
* programs or to the documentation contained in these books. The authors *
* and publisher shall not be liable in any event for incidental or *
* consequential damages in connection with, or arising out of, the *
* furnishing, performance, or use of these programs. *
**************************************************************************/