c-resources/CPlusPlus20ForProgrammers-m.../examples/ch14/fig14_17.cpp

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// fig14_17.cpp
// Demonstrating projections with C++20 range algorithms.
#include <array>
#include <algorithm>
#include <fmt/format.h>
#include <iostream>
#include <iterator>
#include <string>
#include <string_view>
class Employee {
public:
Employee(std::string_view first, std::string_view last, int salary)
: m_first{first}, m_last{last}, m_salary{salary} {}
std::string getFirst() const {return m_first;}
std::string getLast() const {return m_last;}
int getSalary() const {return m_salary;}
private:
std::string m_first;
std::string m_last;
int m_salary;
};
// operator<< for an Employee
std::ostream& operator<<(std::ostream& out, const Employee& e) {
out << fmt::format("{:10}{:10}{}",
e.getLast(), e.getFirst(), e.getSalary());
return out;
}
int main() {
std::array employees{
Employee{"Jason", "Red", 5000},
Employee{"Ashley", "Green", 7600},
Employee{"Matthew", "Indigo", 3587}
};
std::ostream_iterator<Employee> output{std::cout, "\n"};
std::cout << "Employees:\n";
std::ranges::copy(employees, output);
// sort Employees by salary; {} indicates that the algorithm should
// use its default comparison function
std::ranges::sort(employees, {},
[](const auto& e) {return e.getSalary(); });
std::cout << "\nEmployees sorted in ascending order by salary:\n";
std::ranges::copy(employees, output);
// sort Employees by salary in descending order
std::ranges::sort(employees, std::ranges::greater{},
&Employee::getSalary);
std::cout << "\nEmployees sorted in descending order by salary:\n";
std::ranges::copy(employees, output);
}
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