arrays and command lines....again

[afleury1]

I posted earlier today with my code dilemma, but was completely confused about what was supposed to be the resulting output and how the user was to enter the information

So, here are my problems

when user enters:

./combinations -r 8 -n 3
output is:
Iterative total = 0.00014881
Time spent in microseconds:97
Recursive total= 0
Time spent in microseconds: 5
**this is wrong it is suppose to error check for when n < r

when user enters:
./combinations -r 50 -n 8
output is:
Iterative total = 2.50543e+09
Time spent in microseconds:98
**It is not giving the recursive information

when user enters:
./combinations -r left blank -n 7
Output is:
Please enter the values in this format: ./combinations [-n <number>] [-r <number>]
** This is correct output

when user enters:
./combinations -r 9 -n left blank
output is:
Please enter the values in this format: ./combinations [-n <number>] [-r <number>]
** This is correct output

when user enters non numbers for either -r or -n program runs as if both were numbers.

How do I error check for:

negatives, non-numbers, and when n < r

How do I fix the part when r is less than n it printouts both iterative and recursive information

I would like to make the error messages as functions to avoid repetitive coding.

  #include<iostream> 
#include<sys/time.h> 
#include<cstdlib> 

using namespace std; 

     long double factorial(long double n); 
     long double iterative_func(long double n, long double r); 
     long double recursive_func(long double n, long double r); 
     long double myfunction(long double n, long double r); 

   
int main(int argc, char* argv[]) 
{ 
         int n = 0; //-n 
         int r = 0; //-r 

// checking for -n or -r 
         if (argc == 5) 
        { 
            if(argv[1][0] == '-' && argv[1][1] == 'n') 
            { 
                n = atoi(argv[2]); 

           if(argv[3][0] == '-' && argv[3][1] == 'r') 
                r = atoi(argv[4]); 

          else 
          { 
              cout << "Please enter values in this format: ./combinations [-r <number>] [-n <number>]" << endl; 

              return 0; 
          } 
     } 
// - r, - n 
     else if(argv[1][0] == '-' && argv[1][1] == 'r') 
    { 
          r = atoi(argv[2]); 
       
         if(argv[3][0] == '-' && argv[3][1] == 'n') 
               n = atoi(argv[4]); 
         else 
        { 
             cout<< "Please enter values in this format: ./combinations [-r <number>] [-n <number>]" << endl; 
             return 0; 
         } 
    } 
    else 
    { 
        cout<< "Please enter values in this format: ./combinations [-r <number>] [-n <number>]" << endl; 
        return 0; 
     } 
  } 

     else 
     { 
             cout << "Please enter values in this format: ./combinations [-r <number>] [-n <number>]" << endl; 
              return 0; 
      } 
//calling myfunction 
   
           myfunction(n, r); 
 
      return 0; 
}

long double myfunction(long double n, long double r)
 {
         long double result1, result2;

                 typedef struct timeval time;
                 time stop, start;

                 gettimeofday(&start, NULL);

                 result1 = iterative_func(n, r);
                 cout<< "Iterative total = "<< result1<<endl;

                 gettimeofday(&stop, NULL);

                 if (stop.tv_sec > start.tv_sec)
                    cout<< "Time spent in seconds: "<< stop.tv_sec- start.tv_sec << endl;
                 else
                    cout << "Time spent in microseconds:"<< stop.tv_usec - start.tv_usec << endl;

                 gettimeofday(&start, NULL);

 result2 = recursive_func(n, r);
                 cout<< "Recursive total= "<< result2 << endl;

                 gettimeofday(&stop, NULL);

                 if (stop.tv_sec > start.tv_sec)
                    cout << "Time spent in seconds: " << stop.tv_sec - start.tv_sec << endl;
                 else
                    cout << "Time spent in microseconds: "<< stop.tv_usec - start.tv_usec <<     endl;
                 return 0;
 }

 long double factorial(long double n)
 {
         long double total = 1;
         long double i;

         for (i = 1; i <= n; i++)
         {
                 total *= i;
         }
         return total;
 }

 long double recursive_func(long double n, long double r)
 {
         if(r < 0 || r > n)
            return 0;
         if (r < 1 || n == r)
            return 1;
         else
            return recursive_func(n-1, r) + recursive_func(n-1, r-1);
 }

 long double iterative_func(long double n, long double r)
 {
         long double total = 1;

         total = factorial(n)/(factorial(r) * factorial(n - r));
         return total;
 }

[afleury1]

Just trying to do the error check for negative numbers for n. Added and if/ else, if compiles but doesnt work:

int main(int argc, char* argv[]) 
 { 
          int n = 0; //-n 
          int r = 0; //-r 
         char input[MaxChars]; 

 // checking for -n or -r 
 
           if (argc == 5) 
          {  
                if(argv[1][0] == '-' && argv[1][1] == 'n') 
                { 
                        if(n < 0)   // added this code to check for negative n, is not doing it though
                       { 
                            cout<< "Please enter positive numbers only."<< endl; 
                            return 0; 
                      }
                      else   // else for the error checking.....
                     { 
                            n = atoi(argv[2]); 
                      } 
             if(argv[3][0] == '-' && argv[3][1] == 'r') 
                   r = atoi(argv[4]); 

             else 
             { 
                      cout << "Please enter the values in the following format: ./combination s [-n (number) -r (number)]" << endl; 
                      return 0; 
              } 
     }

output:
./combinations -r 6 -n -9
Iterative total = 0.00138889
Time spent in microseconds:98
Recursive total= 0
Time spent in microseconds: 6