Question

Possible Duplicate:
How to convert a single char into an int

Well, I’m doing a basic program, wich handles some input like:

2+2

So, I need to add 2 + 2.

I did something like:

string mys "2+2";
fir = mys[0];
sec = mys[2];

But now I want to add “fir” to “sec”, so I need to convert them to Int.
I tried “int(fir)” but didn’t worked.

Answer 1

There are mulitple ways of converting a string to an int.

Solution 1: Using Legacy C functionality

int main()
{
    //char hello[5];     
    //hello = "12345";   --->This wont compile

    char hello[] = "12345";

    Printf("My number is: %d", atoi(hello)); 

    return 0;
}

Solution 2: Using lexical_cast(Most Appropriate & simplest)

int x = boost::lexical_cast<int>("12345"); 

Solution 3: Using C++ Streams

std::string hello("123"); 
std::stringstream str(hello); 
int x;  
str >> x;  
if (!str) 
{      
   // The conversion failed.      
}