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#include <iostream>
#include <vector>
#include <exception>
///Prime Number Calculator
class primes
{
std::vector<int> primeNumbers; //the vector that will hold the prime numbers (not to be confused with the object which is singular)
bool primechecker (int b); //checks for prime-ness
void primedisplayer (int o); //displays the number sent to it, which should be prime (if not, something is horribly, horribly wrong)
void setVector (int l); //assigns that new-found prime number to the vector that holds the prime numbers
public:
int numberPrimes; //the number of primes that the user wants
bool memoryException = false; //whether the user's computer has enough memory to keep this running
void calculatePrimes(); //the for loop that everything runs in
primes (int); //the constructor
};
primes::primes(int a) //constructor, for simplicity's sake
{
numberPrimes = (a-1); //assigns whatever value you send it to the number of primes you want
}
bool primes::primechecker(int b)
{
bool test = false;
for(std::vector<int>::iterator i = primeNumbers.begin();
i != primeNumbers.end();
i++) //iteratres through the vector of primes
{
if(b % *i == 0)
{
test = true; //if the number isn't prime, set test to true and exit the loop.
break; //no need to check every single other number once you know it isn't prime
}
}
return test; //return whether the number is prime or not
}
void primes::calculatePrimes() //the function where it all takes place
{
int m = 2; //make sure it starts checking primes at 2 as well
primedisplayer(m); //this is so it starts off with 2
try //it's a vector, so exception-handling is mandatory
{
primeNumbers.emplace_back(2); //make the first prime number in the vector
}
catch(std::bad_alloc&)
{
std::cout << "Error: No memory to allocate initial value to vector. Exiting...";
memoryException = true;
}
if (memoryException == true) //if there is no memory to assign 2 to the vector
numberPrimes = 0; //make it so the for loop will never run
for(int i = 0; i < numberPrimes; i++)
{
while(primechecker(m) == true)
m++; //as long as the number isn't prime, add 1 to it
setVector(m); //when the number is prime, add it to the vector
if(memoryException == true) //if an error occured in memory
break; //exit out
primedisplayer(m); //displays the current value of m
}
return;
}
void primes::setVector(int l)
{
try
{
primeNumbers.emplace_back(l); //add the prime number to the end of the vector of prime numbers
}
catch(std::bad_alloc&)
{
std::cout << "Error: Ran out of memory during allocation of new prime number to array.";
memoryException = true; //set the error check to true if there's no memoroy left, so the program can exit
}
return;
}
void primes::primedisplayer(int o)
{
std::cout << o << std::endl; //displays the current value of m, which is the just-calculated prime number
return;
}
int main()
{
int j; //number of prime numbers.
std::cout << "Please enter the number of prime numbers you want, starting with 2. Enter 0 to\nexit.\n";
std::cin >> j; //get input
std::cout << "\n"; //who doesn't like new lines?
while(true)
{
if (j > 0) //if it's greater than 0, run the program
{
primes primeNumber(j); //create the object, calling the constructer with the inputted number (if valid)
primeNumber.calculatePrimes(); //then calls the function to get the ball rolling
break; //then exits the loop when complete
}
else if(j < 0) //if it's less than 0, ask again
{
std::cout << "Number is less than zero. Please try again.\n";
std::cin >> j;
std::cout << "\n"; //with another complimentary new line (I mean really, can you ever go wrong with new lines?)
}
else //if it's zero, exit out (or if it's invalid input, like a letter)
break;
}
return 0;
}
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