C++ using function pro

Avoid stupid C++ behavior in case of overflow

#include 

#include

#include 

#include 

int fermattest (int n) 

{

  int a, result, i;

  a = rand() % n;

  cout << "Trying with " << a << endl;

 return (a == (int(pow(a,n)) % n)); 

  result = 1;

  i = n;

  while (i > 0) 

  {

    result = (result * a) % n;

    i = i-1;

  }

  return (a == result);

}

int main () 

 {

  int n, i;

  cout << "Enter a natural number: ";

  cin >> n;

  cout << "How many trials?: ";

  cin >> i;

  srand(n*i);

  while (i > 0) 

  {

    if (fermattest(n)) 

    {

      i = i-1;

    } 

    else 

    {

      cout << "The number " << n << " is definitely not prime." << endl;

      return(0);

    }

  }

  cout << "The number " << n << " is probably prime." << endl;

  return(0);

}

Understanding call-by-value and call-by-reference

#include 

#include

int f1 (int, int, int);

int f2 (int&, int&, int&);

int f3 (int, int&, int);

void main () 

{

  int i, j, k;

  i=1;

  j=2;

  k=3;

  cout << endl;

  cout << "Initial values of i, j, and k are: " 

    << i << ", " << j << ", and " << k << endl << endl;

  cout << "f1(i,j,k) = " << f1(i,j,k) << endl;

  cout << "Values of i, j, and k after the call to f1 are: " 

    << i << ", " << j << ", and " << k << endl << endl;

  cout << "f2(i,j,k) = " << f2(i,j,k) << endl;

  cout << "Values of i, j, and k after the call to f2 are: " 

    << i << ", " << j << ", and " << k << endl << endl;

  cout << "f3(i,j,k) = " << f3(i,j,k) << endl;

  cout << "Values of i, j, and k after the call to f3 are: " 

    << i << ", " << j << ", and " << k << endl;

}

int f1 (int x, int y, int z)

          {

  x=x+5;

  y=y+5;

  z=z+5;

  return(x+y+z);

}

int f2 (int& x, int& y, int& z) 

{

  x=x+5;

  y=y+5;

  z=z+5;

  return(x+y+z);

}

int f3 (int x, int& y, int z) 

{

  x=x+5;

  y=y+5;

  z=z+5;

  return(x+y+z);

}