C++ Classes: Christian Holiday Calculator - c++

Question

Basically, I'm trying to complete this exam-style question for exam practice. I know how to do everything but the last question, to do with classes. I kinda get them, but don't know how to apply it to the question. Could anybody give me some starting points or tips (or even possible answers) to how I would go about creating a C++ class? Any help is much appreciated. The question is below. Apologies about how long it is.
In 1800 the mathematician Carl Friedrich Gauss presented an algorithm for calculating the
date of the Easter holiday in the new Gregorian calendar (introduced in the British Empire in
the year 1752). For this a number of expressions need to be evaluated:
Two terms M and N, which for a given year y hold the values:
year M N
1700-1799 23 3
1800-1899 23 4
1900-2099 24 5
2100-2199 24 6
The expressions are:
a = y mod 19
b = y mod 4
c = y mod 7
d = (19a + M) mod 30
e = (2b + 4c + 6d + N) mod 7
If 22+d+e is smaller than 32 than this sum is the day of the Easter holiday in March.
Otherwise d+e-9 is the day of Easter in April unless:
- the result is the 26th April, in which case Easter is on the 19th April instead
- the result is the 25th April, in which case Easter is on the 18th of April if d is 28 and
a is greater than 10
a) Implement a C/C++ function that given a year as parameter will
print out the date for the Easter holiday. (10 marks)
Other Christian holidays can be calculated from the date of Easter:
Good Friday is the Friday before Easter Sunday.
Palm Sunday is the Sunday before Easter Sunday.
Whit Sunday is 7 weeks after Easter Sunday.
Ascension day is 10 days before Whit Sunday.
Note: April and June are 30 days long, whereas March and May are 31 days long.
b) Design/describe algorithms for identifying the date for the Christian
holidays "Good Friday", "Palm Sunday", "Ascension" and "Whit
Sunday". (no source code is required for this answer) (15 Marks)
The terms M and N in the Easter calculation algorithm described by Gauss can also
be calculated using the following expressions:
k = floor(y/100)
p = floor((13 + 8k)/25)
q = floor(k/4)
M = (15 − p + k − q) mod 30
N = (4 + k − q) mod 7
The floor function rounds down a value – in the maths library math.h this is
available as a C function with the prototype double floor(double);
c) Produce a C++ class to implement a Christian Holiday calculator. It
should have private attributes (member variables) representing the
day, month and year of the date and a private method for
calculating the terms M and N. The default constructor should set
all attributes to 0. It should be possible to change the year using a
set() method and to retrieve day and month using get() methods.
The class should also contain compute methods for the different
holidays – example: computeEaster().

Answer 1

...how I would go about creating a C++ class?
Creating a class is simple:
class foobar
{
public:
private:
};
There! you now have a class foobar. That class can be whatever you want it to be. Fill in the public and private sections as appropriate.
Could anybody give me some starting points or tips...
As for how to use classes on how to solve a given problem, here are the general steps in roughly sequential order:
Identify the requirements of the problem. What needs solving?
Reform those requirements as a list of responsibilities. What does your program have to do to fulfill those requirements?
Group those responsibilities together to form a cohesive class object. How does this class object contribute to the overall solution of the problem? How will this object actually be used?
Express and capture that usage in a unit test for each of those objects. While doing this, you can pretend that that class is already implemented and whatever member functions you need from it is available.
Finally, implement that class so the unit test passes.
One last note, as David's comment already pointed out, copying and pasting the original problem verbatim into your question is a bad idea. People will be (substantially) less inclined to read it through. You can increase the likelihood for a response if you clarified exactly what trouble you're having and cutting out all the irrelevant parts.

Answer 2

So, you are stuck on creating a class. Either you don't know how to create a class at all, or you don't know how to create this specific class.
To create a class at all, use the class keyword: class { int i; };. If you have not yet created any classes in C++, then you may need to retake this or another C++ programming class.
If your problem, instead, is that you don't understand how to translate your professor's class design into C++ code, then you are not nearly as alone as you feel. Translating from ambiguous English design statements to concrete C++ programs is difficult, and is the reason we get paid the big bucks.
Let's go through it step by step.
Produce a C++ class to implement a Christian Holiday calculator.
That sounds easy enough, doesn't it?
class ChristianHolidayCalculator {
};
There, that step is done!.
It should have private attributes (member variables) representing the day, month and year of the date
Do you know what attributes or member variables are? Do you need to check the index of your textbook? Go ahead, I'll wait. ... Oh, you're back! You must have seen that member variables are a collection of variables which are scoped by the class declaration and which spring into existence (as a group) everytime an object of that class is created.
class ChristianHolidayCalculator {
double width;
double height;
double depth;
};
Oh, you thought I would name them "year", "month", and "day"? No, that's your homework, not mine. Since you told us that you know how to do the math, I'll leave the specifics to you.
and a private method for calculating the terms M and N.
There are two more vocabulary words: method and private. Go review your course material for those.
You surely found that a method is a function inside the class scope. Methods are special in that they are invoked only in relation to objects of the class at hand.
As for "private", well, I'll leave that to you. Surely you learned something about classes this year?
class ChristianHolidayCalculator {
double width;
double height;
double depth;
void GuitarTune() {
// Code to tighten strings goes here.
}
};
Since this method has to compute M and N, you'll need someplace to store the results. Hmm, maybe you need more member variables?
Finally, your teacher mentioned set(), get() and compute() methods. This is his shorthand way of telling you which public methods to create. He probably doesn't mean literally int get() { ... }. He probably means that you need to create a group of methods, all similar in name and in design:
class ChristianHolidayCalculator {
double width;
double height;
double depth;
void GuitarTune() {
// Code to tighten strings goes here.
}
int getRed() { /* return red value */ }
int getGreen() { /* return green value */ }
int getBlue() { /* return blue value */ }
void setRed(int newRed) { /* assign red value */ }
void setGreen(int newGreen) { /* guess */ }
... calculateEaster() ... { ... }
};
There is how you start to create the class. I hope this gives the push you need to get started. Good luck on your exams.