## Function that calculates the factorial of a number
## Usage : f=factorial(n)

function f=factorial(n)
  
  ## Initialize the output
  f=1;
  
  ## Check whether the input is correct
  if ( (n<0) || (rem(n,1)~=0) ) 
    printf("n cannot be a negative number. Exiting...\n");
    return
  endif
  
  for num=1:n
    f*=num;
  endfor
  
endfunction
