将 C++ 字符串变量转换为 long
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Convert C++ string variable to long
提问by kunal18
I have a variable:
我有一个变量：
string item;
It gets initialized at run-time. I need to convert it to long. How to do it? I have tried atol() and strtol() but I always get following error for strtol() and atol() respectively:
它在运行时被初始化。我需要将其转换为long。怎么做？我试过 atol() 和 strtol() 但我总是分别得到以下 strtol() 和 atol() 错误：
cannot convert 'std::string' to 'const char*' for argument '1' to 'long int strtol(const char*, char**, int)'
cannot convert 'std::string' to 'const char*' for argument '1' to 'long int atol(const char*)'
回答by log0
c++11:
C++11：
long l = std::stol(item);
http://en.cppreference.com/w/cpp/string/basic_string/stol
http://en.cppreference.com/w/cpp/string/basic_string/stol
C++98:
C++98：
char * pEnd;.
long l = std::strtol(item.c_str(),&pEnd,10);
回答by Ivan Kruglov
Try like this:
像这样尝试：
long i = atol(item.c_str());
回答by ApprenticeHacker
Use a string stream.
使用字符串流。
#include <sstream>
// code...
std::string text;
std::stringstream buffer(text);
long var;
buffer >> var;
回答by Daniele Pallastrelli
If you don't have access to C++11, and you can use the boost library, you can consider this option:
如果你无权使用C++11，并且可以使用boost库，可以考虑这个选项：
long l = boost::lexical_cast< long >( item );
