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Technical Information Database TI2183C.txt Output Numbers with Thousands Separator Category :General Platform :All Product :C/C++ All Description: How do I output comma-formatted numbers such as 1,000,000 with C++ IOStreams? As common as this would seem, C++ IOStreams have no support for this. The function shown in the code sample below serves two purposes: it converts the long to a string and inserts commas every three digits. Adding the commas during the conversion is much easier than converting the long to a string using sprintf() and then modifying the string. For new programmers, this code is an excellent example use of the modulus operator to reverse a string. The reversing algorithm is almost identical to the generic reverse() function in the Standard Template Library. #include const char *commaStr(unsigned long number) { const int size = 15; // max number of digits static char str[size]; // string to return char *ptr1, *ptr2; // place holders char tempStr[size]; // workplace int counter = 0; // three's counter ptr1 = tempStr; do { // grab rightmost digit and add value of character zero *ptr1++ = (char)(number % 10) + '0'; // strip off rightmost digit number /= 10; // if moved over three digits insert comma into string if (number && !(++counter % 3)) *ptr1++ = ','; // continue until number equal zero } while(number); // this loop reverses characters in a string for( --ptr1, ptr2 = str; ptr1 >= tempStr; --ptr1) *ptr2++ = *ptr1; // add the zero string terminator *ptr2 = '0'; return str; } // simple main to test function int main() { cout <<'s "Toolbox". If you're new to programming, it will be worth your time to run the code in the debugger and watch how it works. Use Debug|Evaluate|Modify to see how the modulus works. Then inspect the pointer in the reverse code to understand how it accomplishes its task. CAVEATS ======= N/A BIBLIOGRAPHY ============ N/A Reference: 7/2/98 10:40:36 AM |
Get easy-to-understand information on the modern and professional ways to convert integer to String C++ from this recent blog post.
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