cccsbuffet / pk_times_table

Nested Loops plus iomanip

Project 2 - Times Table with Nested Loop

This project introduces nested (for) loops and iomanip skills. It also requires use of const.

Requirements Embedded in Text

To encourage you to read and understand this specification, certain requirements are embedded in the text without being called out as such. Failure to fulfill these requirements will drop your grade.

Helpful Pointers to the Zybook

You should read and do these chapters. Use them as a resource.

Concept	Chapter
const	Refer to class
for loop	4.4, 4.5
iomanip	9.2
nested loops	4.7

iomanip

Read chapter 9.2 in the zybook.

#include <iomanip>

The features found in iomanip are helpers for working with streams like cout. These helpers are designed to make formatting output easier. For example:

cout << 1 << " item" << endl;
cout << 10 << " items" << endl;
cout << 100 << " items" << endl;

produces this:

1 item
10 items
100 items

Suppose you wanted to line things up a little more nicely.

cout << setw(4) << 1 << " item" << endl;
cout << setw(4) << 10 << " items" << endl;
cout << setw(4) << 100 << " items" << endl;

produces:

   1 item
  10 items
 100 items

Here, the digits are right justified within four columns / spaces as specified by setw(4).

Perhaps you wanted left justification?

cout << left << setw(4) << 1 << " item" << endl;
cout << setw(4) << 10 << " items" << endl;
cout << setw(4) << 100 << " items" << right << endl;

produces:

1    item
10   items
100  items

Each number still fits in 4 columns but is now left justified.

Notice how setw() must be used set set the width of the next item to be printed but left and right are sticky - they remain in force until changed.

Nested loops

Read and do chapter 4.7 in your zybook.

Loops can be found inside other loops. When this happens, they are called nested loops.

The inner most loop can be thought of as happening the fastest. The outer most loop can be thought of as happened the slowest. Imagine an odometer in a car. The one's digit (or tenths on some cars) is the innermost, and cycles quickly compared to the digit to its left.

Example:

for (int outer = 0; outer < 10; outer++) {
	for (int inner = 0; inner < 10; inner++) {
		cout << outer << " " << inner << endl;
	}
}

The inner loop will run 100 times (10 x 10).

Times table

For this project, print a nicely formatted 10 x 10 times table:

hyde pk_times_table $> ./a.out
    |   1   2   3   4   5   6   7   8   9  10
----+----------------------------------------
  1 |   1   2   3   4   5   6   7   8   9  10
  2 |   2   4   6   8  10  12  14  16  18  20
  3 |   3   6   9  12  15  18  21  24  27  30
  4 |   4   8  12  16  20  24  28  32  36  40
  5 |   5  10  15  20  25  30  35  40  45  50
  6 |   6  12  18  24  30  36  42  48  54  60
  7 |   7  14  21  28  35  42  49  56  63  70
  8 |   8  16  24  32  40  48  56  64  72  80
  9 |   9  18  27  36  45  54  63  72  81  90
 10 |  10  20  30  40  50  60  70  80  90 100

There will be at most four loops in this program. Use the first to print the horizontal heading.

For the dividing horizontal line, you might use your second loop. You can "season this to taste" - that is, once you've gotten the first line right you can code up the dividing line so that it "looks right" but remember to avoid magic numbers.

You might also avoid the second loop using features of iomanip to easily print a calculated number of dashes.

Then, the final two loops are nested loops - the outer will be the rows, the inner will be the columns.

Use setw() with a cell width set to 4 using a const int. For the maximum loop values, also use const int variables. This is to get you in the habit of avoiding magic numbers.

const int CELL_WIDTH = 4;
const int MIN_VALUE = 1;
const int MAX_VALUE = 10;

Now you can say setw(CELL_WIDTH) each time you want to set a width of 4. The advantage of naming what would otherwise be repeated use of magic numbers is so to make your program easier to understand as well as make your program easier to chance. If, for example, you wanted to have a cell spacing of 5 instead of 4, you'd simply change the one line where CELL_WIDTH is set rather than every line where setw() is used.

Notice the first column (coming before the products and the "|" has one fewer characters... again, avoid magic numbers).

Similarly, you might specify a for loop like so:

for (int counter = 1; counter < 10; counter++)

But the use of 1 and 10 as literals make them "magic numbers".

Instead, it is better to write something like:

for (int counter = MIN_VALUE; counter < MAX_VALUE; counter++)

where MIN_VALUE and MAX_VALUE are defined above.

Recall that for loops are described in chapters 4.4 and 4.5.

Work Rules

Work is to be done solo.

What to Hand In

Just your .cpp file via Schoology.

int versus int32_t

You can use either in the project but I hope you'll get in the habit of using the precise form of specifying integer types. In the future, use of the precise integer types will be required.

Setting Expectations

Including some blank lines but no comments, my solution is less than 30 lines. I include this NOT as a challenge but to set your expectations. Should you find yourself writing hundreds of lines, you should reconsider what you're doing.