C++ 字符串到双重转换

问题描述

通常，当我用 C++ 编写任何东西并且需要将 char 转换为 int 时，我只需创建一个新的 int 等于字符.

Usually when I write anything in C++ and I need to convert a char into an int I simply make a new int equal to the char.

我使用了代码(片段)

 string word;  
 openfile >> word;
 double lol=word;

我收到错误

Code1.cpp cannot convert `std::string' to `double' in initialization 

错误究竟是什么意思?第一个词是数字 50.谢谢:)

What does the error mean exactly? The first word is the number 50. Thanks :)

推荐答案

你可以很容易地将 char 转换为 int ，反之亦然，因为对于机器来说 int 和 char 是相同的，8 位，唯一的区别在于它们必须显示在屏幕上，如果数字是 65 并保存为字符，则显示'A'，如果保存为整数，则显示 65.

You can convert char to int and viceversa easily because for the machine an int and a char are the same, 8 bits, the only difference comes when they have to be shown in screen, if the number is 65 and is saved as a char, then it will show 'A', if it's saved as a int it will show 65.

对于其他类型，情况会发生变化，因为它们在内存中的存储方式不同.C 中有一个标准函数可以让你轻松地从字符串转换为双精度，它是 atof.(你需要包含 stdlib.h)

With other types things change, because they are stored differently in memory. There's standard function in C that allows you to convert from string to double easily, it's atof. (You need to include stdlib.h)

#include <stdlib.h>

int main()
{
    string word;  
    openfile >> word;
    double lol = atof(word.c_str()); /*c_str is needed to convert string to const char*
                                     previously (the function requires it)*/
    return 0;
}

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