6.6. Encapsulation and generalization¶
Encapsulation usually means taking a piece of code and wrapping it up in
a function, allowing you to take advantage of all the things functions
are good for. We have seen two examples of encapsulation, when we wrote
printParity in Section [alternative] and
isSingleDigit in Section [bool].
Generalization means taking something specific, like printing multiples of 2, and making it more general, like printing the multiples of any integer.
Here’s a function that encapsulates the loop from the previous section
and generalizes it to print multiples of n.
void printMultiples (int n) {
int i = 1;
while (i <= 6) {
cout << n * i << " ";
i = i + 1;
}
cout << endl;
}
To encapsulate, all I had to do was add the first line, which declares
the name, parameter, and return type. To generalize, all I had to do was
replace the value 2 with the parameter n.
If we call this function with the argument 2, we get the same output as before. With argument 3, the output is:
3 6 9 12 15 18
and with argument 4, the output is
4 8 12 16 20 24
By now you can probably guess how we are going to print a multiplication
table: we’ll call printMultiples repeatedly with different
arguments. In fact, we are going to use another loop to iterate through
the rows.
int i = 1;
while (i <= 6) {
printMultiples (i);
i = i + 1;
}
First of all, notice how similar this loop is to the one inside
printMultiples. All I did was replace the print statement with a
function call.
Try running the active code below, which uses printMultiples.
The output of this program is
1 2 3 4 5 6
2 4 6 8 10 12
3 6 9 12 15 18
4 8 12 16 20 24
5 10 15 20 25 30
6 12 18 24 30 36
which is a (slightly sloppy) multiplication table. If the sloppiness bothers you, you can also use tab characters, like below.
The active code below uses tab characters to make the table neater.
- Replacing integers with parameters.
- This may be a possible way to generalize, but not the purpose.
- Using a parameter that exists in several different functions.
- This is not the purpose of generalization.
- Taking a very specific task and making it more applicable to other situations.
- This makes your code more versatile.
- Creating two functions with the same purpose but different names.
- This is not the purpose of generalization.
Q-3: What is the purpose of generalization?
Create a function called powersOfTwo which prints out a table with the powers of two up to \(2^{5}\).
Now let’s generalize the function to print out the powers of a parameter n up to \(n^{5}\). Create a
function called powersOfn which takes an int n as a parameter.