EX2 ANSWER

```include/temperature.h
#pragma once

/**
 * Convert Celsius to Fahrenheit
 * Formula: F = C * 9/5 + 32
 */
double celsiusToFahrenheit(double celsius);

/**
 * Convert Fahrenheit to Celsius
 * Formula: C = (F - 32) * 5/9
 */
double fahrenheitToCelsius(double fahrenheit);

```
``` rsc/temperature.cpp
#include "temperature.h"

double celsiusToFahrenheit(double celsius) {
    return celsius * 9.0 / 5.0 + 32.0;
}

double fahrenheitToCelsius(double fahrenheit) {
    return (fahrenheit - 32.0) * 5.0 / 9.0;
}
```

``` cmakelists.txt
cmake_minimum_required(VERSION 3.15)

project(TemperatureConverter VERSION 1.0)

# 创建静态库
add_library(templib STATIC
    src/temperature.cpp
)

# 为库设置包含目录（PUBLIC 使得链接该库的目标也能访问）
target_include_directories(templib PUBLIC include/)

# 创建可执行文件
add_executable(tempconv main.cpp)

# 链接库到可执行文件
target_link_libraries(tempconv PRIVATE templib)

# 设置 C++ 标准
set_property(TARGET templib PROPERTY CXX_STANDARD 17)
set_property(TARGET tempconv PROPERTY CXX_STANDARD 17)

```
``` main.cpp
#include <iostream>
#include <iomanip>
#include "temperature.h"

void displayMenu() {
    std::cout << "\nTemperature Converter" << std::endl;
    std::cout << "=====================" << std::endl;
    std::cout << "1. Celsius to Fahrenheit" << std::endl;
    std::cout << "2. Fahrenheit to Celsius" << std::endl;
    std::cout << "3. Exit" << std::endl;
    std::cout << "\nChoose an option: ";
}

int main() {
    int choice;
    double temperature;
    
    // 设置输出精度
    std::cout << std::fixed << std::setprecision(1);
    
    while (true) {
        displayMenu();
        std::cin >> choice;
        
        if (choice == 3) {
            std::cout << "Goodbye!" << std::endl;
            break;
        }
        
        if (choice == 1) {
            std::cout << "Enter temperature in Celsius: ";
            std::cin >> temperature;
            double result = celsiusToFahrenheit(temperature);
            std::cout << temperature << "°C = " << result << "°F" << std::endl;
        } else if (choice == 2) {
            std::cout << "Enter temperature in Fahrenheit: ";
            std::cin >> temperature;
            double result = fahrenheitToCelsius(temperature);
            std::cout << temperature << "°F = " << result << "°C" << std::endl;
        } else {
            std::cout << "Invalid option. Please try again." << std::endl;
        }
    }
    
    return 0;
}
```