How do you convert a C++ string to an int? [duplic

Question

Possible Duplicate:
How to parse a string to an int in C++?

How do you convert a C++ string to an int?

Assume you are expecting the string to have actual numbers in it ("1", "345", "38944", for example).

Also, let's assume you don't have boost, and you really want to do it the C++ way, not the crufty old C way.

Answer 1

#include <sstream>

// st is input string
int result;
stringstream(st) >> result;

Answer 2

Use atoi

Answer 3

Perhaps I am misunderstanding the question, by why exactly would you not want to use atoi? I see no point in reinventing the wheel.

Am I just missing the point here?

Answer 4

I have used something like the following in C++ code before:

#include <sstream>
int main()
{
    char* str = "1234";
    std::stringstream s_str( str );
    int i;
    s_str >> i;
}

Answer 5

C++ FAQ Lite

[39.2] How do I convert a std::string to a number?

https://isocpp.org/wiki/faq/misc-technical-issues#convert-string-to-num

Answer 6

Let me add my vote for boost::lexical_cast

#include <boost/lexical_cast.hpp>

int val = boost::lexical_cast<int>(strval) ;

It throws bad_lexical_cast on error.