C++ 函数 stoi 未声明
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Function stoi not declared
提问by user3258512
I'm trying to use stoito convert a string to an integer, however it says it's not declared. I have the standard library and the <string>included, but it still says [Error] 'stoi' was not declared in this scope
我正在尝试stoi将字符串转换为整数，但是它说它没有声明。我有标准库和<string>包含的库，但它仍然说[Error] 'stoi' was not declared in this scope
The code is the following:
代码如下：
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string>
using namespace std;
int main()
{
string end, init;
cout << "Introduction" << endl;
cout << "Start time (xx:yy)" << endl;
cin >> init;
string hours0 = init.substr(0,2);
int hours = stoi(hours0);
cout << hours << endl;
system("pause");
return 0;
}
Either tell me why it isn't working, or give me a second option to do it, please.
请告诉我为什么它不起作用，或者请给我第二个选择。
回答by Captain Obvlious
回答by Eamonn Kenny
The answers above are correct, but not well explained.
上面的答案是正确的，但没有很好地解释。
g++ -std=c++11 my_cpp_code.cpp
Add -std=c++11 to your compiler options since you are most likely using an older version of debian or ubuntu which is not using by default the new c++11 standard of g++/gcc. I had the same problem on Debian Wheezy.
将 -std=c++11 添加到您的编译器选项中，因为您很可能使用的是旧版本的 debian 或 ubuntu，它们默认不使用 g++/gcc 的新 c++11 标准。我在 Debian Wheezy 上遇到了同样的问题。
http://en.cppreference.com/w/cpp/string/basic_string/stol
http://en.cppreference.com/w/cpp/string/basic_string/stol
shows in really small writing to the right in green that c++11 is required.
以非常小的绿色文字在右侧显示需要 c++11。
回答by nneonneo
stoiis a C++11 function. If you aren't using a compiler that understands C++11, this simply won't compile.
stoi是一个 C++11 函数。如果您使用的不是理解 C++11 的编译器，这将无法编译。
You can use a stringstreaminstead to read the input:
您可以使用 astringstream来读取输入：
stringstream ss(hours0);
ss >> hours;
回答by Daniel
stoi is available "since C++11". Make sure your compiler is up to date.
stoi 可用“自 C++11”。确保您的编译器是最新的。
You can try atoi(hours0.c_str()) instead.
你可以试试 atoi(hours0.c_str()) 代替。
回答by pistol_pete
instead of this line -
而不是这条线 -
int hours = stoi(hours0);
int hours = stoi(hours0);
write this -
写这个——
int hours = atoi(hours0.c_str());
int hours = atoi(hours0.c_str());
Reference : int atoi(const char *str)
回答by M.M
In comments under another answer, you indicated you are using a dodgy version of g++under MS Windows.
在另一个答案下的评论中，您表示您使用的是g++MS Windows 下的狡猾版本。
In this case, -std=c++11as suggested by the top answer would still not fix the problem.
在这种情况下，-std=c++11正如最佳答案所建议的那样仍然无法解决问题。
Please see the following thread which does discuss your situation: std::stoi doesn't exist in g++ 4.6.1 on MinGW
请参阅以下讨论您的情况的线程：std::stoi 在 MinGW 上的 g++ 4.6.1 中不存在
回答by Doug
#include <algorithm>
Include this and then you can compile it using...
包括它，然后您可以使用...
g++ -Wall -std=c++11 test.cpp -o test
g++ -Wall -std=c++11 test.cpp -o test
You can also add "cd /d %~dp0" as the first line of a .bat file in the same directory as your source file so all you have to do is double click on the .bat file for an "automated" compilation.
您还可以将“cd /d %~dp0”添加为源文件所在目录中 .bat 文件的第一行，这样您只需双击 .bat 文件即可进行“自动”编译。
Hope this helps!
希望这可以帮助！
回答by Riya Arora
Install the latest version of TDM-GCC here is the link-http://wiki.codeblocks.org/index.php/MinGW_installation
在这里安装最新版本的 TDM-GCC 是链接 - http://wiki.codeblocks.org/index.php/MinGW_installation
回答by Sisnett
Are you running C++ 11? stoi was added in C++ 11, if you're running on an older version use atoi()
你在运行 C++ 11 吗？stoi 是在 C++ 11 中添加的，如果您在旧版本上运行，请使用 atoi()
回答by Nassima Noufail
Add this option: -std=c++11while compiling your code
添加此选项：-std=c++11在编译代码时
g++ -std=c++11 my_cpp_code.cpp
