C++大数模版-面向对象实现

借鉴了一下比较规范的大数运算C++库，写了一套面向对象的大数运算库。存在的一点不足是下面的代码最低运行环境是C++11,如果不是的话，std::to_string()这个函数需要自己实现，再有函数式运算的办法还是比较麻烦，重载运算符会好一点。下面是加法的版本：

#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>

class Bignumber{
public:
    explicit Bignumber(std::string number);
    Bignumber add(Bignumber other){
        std::string result;
        int diflen = this->string_var.length() - other.string_var.length();
        if(diflen>0){
            for(int j=0;j<diflen;j++)
                other.string_var.insert(0, "0");
        } else{
            for(int j=diflen;j<0;j++)
                this->string_var.insert(0, "0");
        }
        int carry=0;
        for(int i=this->string_var.length()-1; i>=0; –i){
            int sum = this->string_var[i] + other.string_var[i] + carry - &#039;0&#039; -&#039;0&#039;;
            carry=0;
            if (sum <= 9 || i == 0) {
                result.insert(0, std::to_string(sum));
            }
            else {
                result.insert(0, std::to_string(sum % 10));
                carry = 1;
            }
        }
        if(carry){result.insert(0,"1");}
        return Bignumber(result);
    }
    std::string getstr(){
        return this->string_var;
    }
private:
    std::string string_var;
};
Bignumber::Bignumber(std::string number)
{
    this->string_var = number;
}
int main(){
    std::cout<<Bignumber(std::to_string(21)).getstr()<<std::endl;
    Bignumber a1 = Bignumber("8888888");
    Bignumber b1 = Bignumber("132222222");
    std::cout<<a1.add(b1).getstr();
    return 0;
}