Generate the Norwegian equivalent to social security numbers

This is just a little hobby project I've been working on. I've been using it to learn/improve my knowledge of C++.

The program generate Norwegian personal-numbers (11 digits) for males born a given year. It works just fine, but I'd like some input on how to improve the code. For now I have a basic class structure.

Norwegian personal-numbers is built up like this.

```
#include

using namespace std;

const int DATE_LENGTH = 6;
const int BUFFER = 30;

class ID {
private:
int date[DATE_LENGTH];
int i1, i2, i3;
int k1, k2;
int year;
public:
ID(int i1 = 0, int i2 = 0, int i3 = 0, int k1 = 0, int k2 = 0) {
for (int i = 0; i year = year;
}

int getYear() {
return year;
}

void individSiffer() {
static int individ = -1;
if(year >= 1900 && year <= 1999 ){
individ++;
i1 = i2 = i3 = 0;
}
i3 = individ % 10;
if(individ < 100){
i1 = 0;
i2 = individ / 10 % 10;
}else if(individ < 10){
i1 = i2 = 0;
}else{
i1 = individ / 100 % 10;
i2 = individ / 10 % 10;
}
}

void generate() {
k1 = 11 - ((3date[0] + 7date[1] + 6date[2] + 1date[3] + 8date[4] + 9date[5] + 4i1 + 5i2 + 2*i3) % 11);
if(k1 == 11){
k1 = 0;
}
k2 = 11 - ((5date[0] + 4date[1] + 3date[2] + 2date[3] + 7date[4] + 6date[5] + 5i1 + 4i2 + 3i3 + 2k1) % 11);
if(k2 == 11){
k2 = 0;
}
if((i3 != 0 && i3 != 2 && i3 !=4 && i3 !=6 && i3 !=8) && (k1 != 10 && k2 !=10)){
for (int i = 0; i < DATE_LENGTH; i++) {
printf("%d", date[i]);
}
printf("%d%d%d%d%d\n", i1, i2, i3

Comment on C++ interface:

You are doing work outside of ID that belongs as part of the class:

ID generator;

for(int i = 0; i < DATE_LENGTH; i++){
    *(generator.getDate() + i) = int(dateString[i]-'0');
}

generator.setYear(1900 + (*(generator.getDate() + 4) * 10) + *(generator.getDate() + 5));

while(i < 500){
    generator.individSiffer();
    generator.generate();
    i++;
}

Because this work is not part of a method you are exposing implementation details of your ID class via getter methods. All of which is bad:

A better interface would have been:

std::string date = getDate(); // Get a valid date or throw.
ID          generator(date);

std::cout << generator;

Comments on Code

Don't use this interface.
What happens if the user types an extra long line of stuff.

cin.getline(dateString, BUFFER);

Its not going to crash but you are left with lots of crap on the input stream. User input is line based so read a line from the user and then try and parse the line. Because a line can be any length don't use that version of get line.

std::string line;
while(std::getline(std::cin, line))
{
    // Valid line has been read.
    if (validDate(line))
    {    return line;
    }
    std::cerr << "Invalid date please try again\n";
}
throw std::runtime_error("The user give up trying to enter a date correctly");

Comments on C functions

C based functions for printing printf() are dangerous, because they are not type safe. Prefer to use the C++ type safe streams.

Comments on Data values

generator.setYear(1900 + (*(generator.getDate() + 4) * 10) + *(generator.getDate() + 5));

What about people born after 31st Dec 1999?

Comments on Loop structures

while(i < 500){
    // STUFF
    i++;
}

// This kind of loop is better written as a for:

for(int loop=0; loop < 500; ++loop) {
    // STUFF
}

Also notice that I am declaring my loop variable as close to the point of usage as possible. Do not use the C style of putting all the variables at the top of the function. Put your variables where you can see there declaration and type easily.

StackExchange Code Review Q#55870, answer score: 5