将字符串转换为long [英] Converting string to long

问题描述

我想将字符串转换为long。这听起来很容易，但我仍然得到相同的错误。我试过：

I'm trying to convert a string to long. It sounds easy, but I still get the same error. I tried:

include <iostream>
include <string>    

using namespace std;

int main()
{
  string myString = "";
  cin >> myString;
  long myLong = atol(myString);
}

但总是出现错误：

.../main.cpp:12: error: cannot convert 'std::string {aka std::basic_string<char>}' to 'const char*' for argument '1' to 'long int atol(const char*)'

<
引用说明如下：

occured. The reference says following:

long int atol ( const char * str );

任何帮助？

推荐答案

尝试

long myLong = std::stol( myString );

此函数有三个参数：

long stol(const string& str, size_t *idx = 0, int base = 10);

您可以使用第二个参数来确定字符串中解析数字的位置。例如

You can use the second parameter that to determine the position in the string where parsing of the number was stoped. For example

std::string s( "123a" );

size_t n;

std::stol( s, &n );

std::cout << n << std::endl;

输出为

3

函式可能会抛出异常。

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