use of atoi

[petergrwl]

hi
i have a string xxxxxxxxxxxxxxxxxxx

i am reading the string into a structure of smaller strings, and using substr to parse it.
i need to convert one of those string types to integer.

atoi is not working for me,. any ideas? it says cannot convert std::string to const char*

thanks

[Aakanaar]

It won't take a string, You need to pass it a C style string.
so, say your string is Numbers you need to pass Numbers.c_str() to atoi

Oh, and just in case you didn't know. The string we use is a container made to hold the text. while the C style string is just a null terminated array of characters.

[screw]

Your problem is that you use string but the atoi needs const char *.

int atoi ( const char * str );

You should use the c_str function of the string class. I.e:

string str;
...

int number = atoi(str.c_str());

You should check the conversion!

"Return Value
On success, the function returns the converted integral number as an int value.
If no valid conversion could be performed, a zero value is returned.
If the correct value is out of the range of representable values, INT_MAX or INT_MIN is returned."


http://www.cplusplus.com/reference/clibrary/cstdlib/atoi/

OR

You can read a number directly to an integer variable:

int number;

cin >> number;

[petergrwl]

So, if my string is 16.

typedef A
{
string length;
}A;

A.length = line.substr(x,y)

const char *ptr;
ptr = A.length.c_str();

uint8 num;
num = atoi(ptr);

ptr works ... it shows value = 16, but num dosent show anything,. so atoi is not working, any guesses?

[kbw]

Have you looked at the value of A.length before passing it to atoi? You'll get zero if the string doesn't start with +/- or a number.

[kempofighter]

Please read this. Consider some of the other alternatives before using atoi. If you are already using std::string why not use streams to get the job done?
http://cplusplus.com/forum/articles/9645/