#include "primes.h"
/**********************************************************
This driver has three operations all involving prime
numbers.  This program displays a menu and depending
upon the choice of the user, involkes the approporiate
function. User enters 0 to quit the loop and program.
Author: William martin
Compiled: 1:46:33 AM 2/24/2000
**********************************************************/
/*********************************************************
                FUNCTIONS
**********************************************************/
void primes(int howMany, int startAt);
void howManyPrimes(void);
void howManyFrom(void);
void goldbachsConjecture(void);
void putHeader(void);
void selectionException(void);
/*********************************************************
                MAIN
**********************************************************/
int main(void) {
   int ans;
   while (ans != 0) {
      putHeader();
      scanf("%d", &ans);
      switch (ans) {
         case 0 :
            printf("\n       Have a nice day !");
            break;
         case 1 :
            howManyPrimes();
            continue;
         case 2 :
            howManyFrom();
            continue;
         case 3 :
            goldbachsConjecture();
            continue;
         default  :
            printf("\nWRONG SELECTION: Select1,2,3 or 0 to quit!\n\n\n");
            continue;
      }
   }
   return 0;
}
/**********************************************************
The primes function prints out primes.
Input: integer how many and where to start at.
Output: formatted list of primes
Precondition: user should only use integer input. other
characters involk an infinate loop
***********************************************************/
void primes(int howMany, int startAt ) {
	int i, temp = startAt;
	for (i = 0; i != howMany; ++i) {
		printf("%5d:", i+1);
		while (!is_prime(temp))
      	temp += 1;
		printf(" %d\n", temp);
      temp += 1;
	}
}
/**********************************************************
This function prompts the user for the number of first
primes that they would like printed.
Input: keyboard
Output: sends user defined integer to function primes.
Precondition: user should only use integer input. other
characters involk an infinate loop
***********************************************************/
void howManyPrimes(void) {
	int i, s = 0;
	printf("\nHow many first primes do you want to see ==> ");
	scanf ("%d", &i);
	printf("\n\n");
   primes(i, s);
   return 0;
}
/**********************************************************
This function prompts the user for the number of first
primes and at what index to start at.
Input: keyboard
Output: sends user defined integers to function 'primes'.
Precondition: user should only use integer input. other
characters involk an infinate loop
***********************************************************/

void howManyFrom(void) {
	int i, s;
	printf("\nHow many first primes do you want to see ==> ");
	scanf ("%d", &i);
   printf("\nWhere do you want to start ==> ");
	scanf ("%d", &s);
	printf("\n\n");
   primes(i, s);
   return 0;
}
/**********************************************************
This function gives the Goldbachs conjecture and tests it.
Input: keyboard - user types the upper and lower bound numbers
to test the conjecture.
Output: prints proof that the conjecture is true.
[EXAMPLE: 700 = 17 + 683 ]
***********************************************************/
void goldbachsConjecture(void) {
	int i, j, startP, finishP, testNumber = 0;
	printf("\n\n\n"
          "\nGOLDBACH'S CONJECTURE:"
          "\nEvery even number n > 6 is the sum of two odd primes.\n"
          "\nTo test Goldbach's Conjecture - please submitt starting "
          "\nand ending bounds.  The numbers between the bounds will"
          "\nattempt to prove that the conjecture is true."
          "\n\n"
          "Enter starting point ==> ");
	scanf ("%d", &startP);
   printf("\nWhere do you want to end ==> ");
	scanf ("%d", &finishP);
	printf("\n\n");
   if ((startP%2) != 0)
      ++startP;
   for (i = startP; i <= finishP; i += 2) {
      for (j = 0; !is_prime(testNumber); j++){
         if (is_prime(j))
            testNumber = (i - j);
      }
      j--;
      printf("%5d = %3d +%3d\n", i, j, testNumber);
      testNumber = 0;
   }
}
/**********************************************************
This function displays the menu.
Input: none
Output: prints instructions.
***********************************************************/

void putHeader(void){
	printf("\n"
          "===================================================== \n"
		    "                       PRIMES                         \n"
		    "===================================================== \n"
		    "                                                      \n"
		    "You have three choices to test for primes:            \n"
		    "                                                      \n"
		    "    1 - to specify the number of first primes to view.\n"
		    "    2 - to specify the index and number of primes.    \n"
		    "    3 - to try Goldenbach's conjecture.               \n"
		    "===================================================== \n"
		    "                                                      \n"
		    "Make a selection, (1,2,3) or 0 to quit ==> ");
}
/********************************************************************/