ValidateBirthday

[italo08]

Hi,
I want make validate to birthday have to month 1-12
and the day depends on the days of the month 1-30 or 1-31 or feb 1-29
thank you

[TwilightSpectre]

Make an array with the number of days in each month, and check to see if the given birthday fits for the entry in that month.

[jonnin]

assuming these are unsigned types,
if( month && (month%13 == month) ) //note the +1, so that the mod allows 0-12, right?

you can use a similar check for whatever else you want to test. You can check the months in bulk groups, is it feb, else is it one of the 30s, else its a 31

you can also probably try to put the value into one of the date formatted objects and see if it is valid, I can't remember but its probable that you can catch an error that way.

[rjphares]

From Deitel's book "C++ for Programmers":

class Date 
{
public:
   Date( int = 1, int = 1, int = 1900 ); // default constructor
   void print() const; // print date in month/day/year format
   ~Date(); // provided to confirm destruction order
private:
   int month; // 1-12 (January-December)
   int day; // 1-31 based on month
   int year; // any year

   // utility function to check if day is proper for month and year
   int checkDay( int ) const; 
}; 

#include <iostream>
using std::cout;
using std::endl;

#include "Date.h" // include Date class definition

// constructor confirms proper value for month; calls
// utility function checkDay to confirm proper value for day
Date::Date( int mn, int dy, int yr )
{
   if ( mn > 0 && mn <= 12 ) // validate the month
      month = mn;
   else 
   {                     
      month = 1; // invalid month set to 1
      cout << "Invalid month (" << mn << ") set to 1.\n";
   } // end else

   year = yr; // could validate yr
   day = checkDay( dy ); // validate the day

   // output Date object to show when its constructor is called
   cout << "Date object constructor for date ";
   print();                   
   cout << endl;
} // end Date constructor

// print Date object in form month/day/year
void Date::print() const
{
   cout << month << '/' << day << '/' << year; 
} // end function print

// output Date object to show when its destructor is called
Date::~Date()
{ 
   cout << "Date object destructor for date ";
   print();
   cout << endl;
} // end ~Date destructor

// utility function to confirm proper day value based on 
// month and year; handles leap years, too
int Date::checkDay( int testDay ) const
{
   static const int daysPerMonth[ 13 ] = 
      { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

   // determine whether testDay is valid for specified month
   if ( testDay > 0 && testDay <= daysPerMonth[ month ] )
      return testDay;

   // February 29 check for leap year 
   if ( month == 2 && testDay == 29 && ( year % 400 == 0 || 
      ( year % 4 == 0 && year % 100 != 0 ) ) )
      return testDay;

   cout << "Invalid day (" << testDay << ") set to 1.\n";
   return 1; // leave object in consistent state if bad value
} // end function checkDay 

[jonnin]

or...

<chrono>

month m(value);

if(month.ok()) //this is fairly new, and awesome.
…


this is what I was saying above, but I forgot where to find the function and had to look for a bit.

you will still have to work a little on day.ok() as it just checks to 31, and isn't aware of what month it is. looks like what he needs is month_day.ok () ? I think?

[Thomas1965]

Another option:

bool is_leapyear(int year)
{
  return year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);
}

bool valid_date(int day, int month, int year)
{
  int days[13] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
  
  if (is_leapyear(year))
    days[2] = 29;

  if (month < 1 || month > 12)
    return false;

  return (day >= 1 && day <= days[month]);
}