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Grouping calculations into functions

ddw2003 (2)
Hello all,

I am just starting to learn C++ and I need a hint on how to figure out how to take things out of int main() and grouping them into functions.

The code is completed 
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#include <iostream>
#include <iomanip>

using namespace std;



int main()
{
  int year, month, day;
  char c;
  bool validInput = false;
  while ((cin) && !validInput)
    {
      cout << "Enter a date in the form YYYY-MM-DD: " << flush;
      cin >> year >> c >> month >> c >> day;

      // Check to see if this is a valid date

      // The Gregorian calendar began On Oct 15, 1582. Earlier dates
      // are invalid.

      if (year < 1582)
	validInput= false;
      else if (year == 1582 && month <= 10 && day < 15)
	validInput = false;

      // Months must be in the range 1..12
      else if (month < 1 || month > 13)
	validInput = false;

      // Days must be in the range 1..K where K is the number of
      // days in that month.
      else
	{
	  int numberOfDaysInMonth = 0;
	  switch (month)
	    {
	    case 1:
	    case 3:
	    case 5:
	    case 7:
	    case 8:
	    case 10:
	    case 12:
	      numberOfDaysInMonth = 31;
	      break;

	    case 4:
	    case 6:
	    case 9:
	    case 11:
	      numberOfDaysInMonth = 30;
	      break;

	    case 2:
	      if (((year % 4 == 0) && (year % 100 != 0))
		  || (year % 400 == 0))
		numberOfDaysInMonth = 29;
	      else
		numberOfDaysInMonth = 28;
	    }

	  if (day < 1 || day > numberOfDaysInMonth)
	    validInput = false;
	  else
	    validInput = true;
	}

      if (!validInput)
	{
	  cout << "Sorry, that is not a valid date" << endl;
	  string garbage;
	  getline (cin, garbage); // discard the rest ofthe input line
	}
    }
  if (!cin)
    {
      cout << "Could not obtain valid input." << endl;
      return -1;
    }


  // Input is valid - compute the day number


  // Add up the number of days in all earlier months
  // of this year
  int sum = 0;
  for (int m = 1; m < month; ++m)
    {
      int monthLength = 0;
      switch (m)
	{
	case 1:
	case 3:
	case 5:
	case 7:
	case 8:
	case 10:
	case 12:
	  monthLength = 31;
	  break;

	case 4:
	case 6:
	case 9:
	case 11:
	  monthLength = 30;
	  break;

	case 2:
	  if (((year % 4 == 0) && (year % 100 != 0))
	      || (year % 400 == 0))
	    monthLength = 29;
	  else
	    monthLength = 28;
	}

      sum += monthLength;
    }

  // Then add the day number to that sum
  int dayNum = sum + day;

  cout << setw(2) << setfill('0') << month
       << "/" << setw(2) << setfill('0') << day << "/"
       << setw(4) << year;
  cout << " is day #" << dayNum << " of that year." << endl;

  return 0;
}


I just need to know what to do to take for example:

"A function to compute the day number within the year (returned as an int) given the year, month, and day (passed as int parameters)."

There are others but once I get a hint on how to do this I can figure the rest out. I been stuck on this for days and figure it out for the world LOL!

Thanks for any kind of help.
Zaita (2770)
ddw2003 (2)
Thanks! It makes a bit more sense to me. So that means that my functions have to be before the int main () right?
Zaita (2770)
Only if you don't want to prototype them.
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