sorta stuck...

[pceluvapathy]

so im writing a program to validate isbn, all is good except when i use atoi()with my char* it converts the whole isbn instead of just one number

.bool isbnChk(std::string isbn)
{
//int strElem = 0 ;
/*process the string, stripping non-digits and non 'X' */
for( int strElem = 0 ; strElem < isbn.length() ; strElem ++)
{/*use end iterator*/
if(!isdigit(isbn[strElem]) && toupper(isbn[strElem]) != 'X')
{
isbn.erase(strElem, 1) ;
--strElem ;
//isbn.push_back() ;
}
}

/*create iterator to end of string*/
std::string::reverse_iterator isbnEnd = isbn.rbegin() ;
std::cout << *isbnEnd << std::endl ;
//char *endS = isbn.c_str() ;
 char  *isbnPtr = new char [isbn.length() + 1] ;
std::strcpy(isbnPtr, isbn.c_str()) ;


const int last10 = 9 ;
const int last13 = 12 ;

/*determine if isbn10 || isbn13 if neither throw exception*/
if(isbn.length() == 10)
{
// store and erase last digit as chkDigit if == x then 10
int chkDigit = 0 ;
	if(toupper(isbn[9]) == 'X')
	{
	chkDigit = 10 ;
	printf("%d\n",chkDigit) ;
	}
	else
	{ 
	isbnPtr += last10 ;
	chkDigit = atoi(isbnPtr) ;
	std::cout << "atoi in else : " << atoi(isbnPtr) << std::endl ;
	isbnPtr -= last10 ;
 	printf("in else %d\n",chkDigit) ;
	} 
	//std::cout << *(isbnPtr +1)  << std::endl ;

	
int mult = 1 ; // isbn multiplier, will incriment
int chkSum = 0 ;

char is[14] ;
memcpy(is, isbnPtr, sizeof(isbnPtr)) ;

for(int strElem = 0 ; strElem < last10 ; strElem++)
{
printf("chkSum %d\n", chkSum) ;
chkSum += atoi(isbnPtr) * mult ;
std::cout << "atoi: " << atoi(isbnPtr) << std::endl ;
std::cout << "ISBN: " << *isbnPtr << std::endl ;
++isbnPtr ;
++mult ;
}
chkSum %= 11 ;

printf("%d\n",chkSum) ;
isbn.erase(isbn.length(), 1) ;
} /*end if(isbn10)*/

else if(isbn.length() == 13)
{

} /*end if(isbn13)*/
else
{
// shoot user
}
//std::cout << isbn << std::endl ;
//printf("%s\n",isbn) ;
// strip of nonnum





}

[anhtuanbk57]

It's true that atoi() convert the whole string to number.
Could you make it more clearly?
Is your string contains many numbers which separated by whitespace character?

[pceluvapathy]

I realize that, however is there a way to make isbnPtr point to only one?

[pceluvapathy]

the string is stripped of all non-digits, then converted into a cstring. I need to access one element at a time so i can convert to int's and deal with one at a time.

[anhtuanbk57]

Then use the array operator [] to select each character in your string. Now you have a char and to make it int, subtract it to '0'. Thus:

char testString[] = "12";
cout << testString[0] - '0' << endl;
cout << testString[1] - '0' << endl;

The result is:

1
2