C++編程：tostring的多樣用法

std::to_string 是 C++11 標準庫中的一個函數，用于將數字類型（如 int、float、double 等）轉換為字符串。以下是 std::to_string 的一些常見用法：

1. 將整數轉換為字符串：

#include<iostream>
#include<string>

int main() {
    int num = 42;
    std::string str_num = std::to_string(num);
    std::cout << "Integer: "<< num << ", String: "<< str_num<< std::endl;
    return 0;
}

2. 將浮點數轉換為字符串：

#include<iostream>
#include<string>

int main() {
    double num = 3.14159;
    std::string str_num = std::to_string(num);
    std::cout << "Double: "<< num << ", String: "<< str_num<< std::endl;
    return 0;
}

3. 將浮點數轉換為固定小數位數的字符串：

#include<iostream>
#include <iomanip>
#include <sstream>
#include<string>

std::string to_string_with_precision(const double value, const int precision) {
    std::ostringstream out;
    out<< std::fixed<< std::setprecision(precision)<< value;
    return out.str();
}

int main() {
    double num = 3.14159;
    int precision = 2;
    std::string str_num = to_string_with_precision(num, precision);
    std::cout << "Double: "<< num << ", String (precision "<< precision << "): "<< str_num<< std::endl;
    return 0;
}

4. 將浮點數轉換為科學計數法表示的字符串：

#include<iostream>
#include <iomanip>
#include <sstream>
#include<string>

std::string to_scientific_string(const double value, const int precision) {
    std::ostringstream out;
    out<< std::scientific<< std::setprecision(precision)<< value;
    return out.str();
}

int main() {
    double num = 3.14159;
    int precision = 2;
    std::string str_num = to_scientific_string(num, precision);
    std::cout << "Double: "<< num << ", Scientific String (precision "<< precision << "): "<< str_num<< std::endl;
    return 0;
}

這些示例展示了 std::to_string 和其他相關函數的多樣用法。你可以根據需要調整代碼以適應不同的場景。