int stoi (const wstring& str, sizet idx 0, int base 10) stoi () parses str (first argument) as a number and returns an integer. The function template of stoi () is given below. If you're writing C++, you should do that anyway, but it kind of forces the issue. To convert a string to integer in C++, you can use stoi () function. The biggest expense is that it can throw exceptions, so to use it your code has to be exception-safe. This is almost as simple to use as atoi, but also provides (roughly) the same level of detail in reporting errors as strtol.
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Since you're using C++, you could also consider using boost::lexical_cast. Cheersandhth.-Alf: I agree with you on the part with SO not being an authority, and to an extent with stoi being clear and perhaps the easiest. How to Convert String to Int C++ (And Vice-Versa)Note that strtol does give slightly more detailed results though - in particular, if you got an argument like 123abc, the sscanf call would simply say it had converted a number (123), whereas strtol would not only tel you it had converted the number, but also a pointer to the a (i.e., the beginning of the part it could not convert to a number). Another possibility would be to use sscanf, something like: if (1=sscanf(argv, "%d", &temp)) He also recommended strtol, which is perfectly fine, if a little bit clumsy. The first is clearly meaningful, but the second is a clear error. That's undefined the pointer is uninitialised. atoi has no way to indicate an error, so you get the same return from atoi("0") as you do from atoi("abc"). Simply remove the excess declaration: // convert str to long long int called user3 char endptr NULL user3 strtoll (str.cstr (), &endptr, 10) You have a similar issue with your const char line3, which you declare inside the function, never assign anything to, then construct a string out of. All except atoi reject trailing whitespace.Īs WhirlWind has pointed out, the recommendations to use atoi aren't really very good. All accept leading whitespace check isspace(argv) if you don't want that. The C way simplest, but will treat any invalid number as 0: #include Since this answer was somehow accepted and thus will appear at the top, although it's not the best, I've improved it based on the other answers and the comments.
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