Chapter 15 // Exercise 6, 7 - Principles & Practice Using C++

In this exercise I am using Visual Studio 2017 and modified versions of the graphics files used throughout the chapters. You can find those versions through the link below.

Chapter 15 // Exercise 6, 7

6. Design and implement a bar graph class. Its basic data is a vector<double> holding N values, and each value should represented by a "bar" that is a rectangle where the height represents the value.
7. Elaborate the bar graph class to allow labeling of the graph itself and its individual bars. Allow the use of colour.

Github: https://github.com/l-paz91/principles-practice/tree/master/Chapter%2015/Exercise%206%2C%207

Exercise 6 - The basic bar graph with just bars set to certain heights:

This takes in a vector of doubles and resizes itself depending on the window size. The number of notches are also dependent on the size of the graph and how many bars there are.

Exercise 7 - It's not exactly excel but it'll do. The bars are coloured by random ints so occasional bars may be identical. The notch marking on the Y axis also isn't entirely accurate as it's rounded down in the Axis constructor but whatever. The bar labels and fill colours can be turned off by just providing a bool value and you can set the axis labels to anything once you've created the barchart object.

Chapter 6 // Exercise 9 - Principles & Practice Using C++

Chapter 6 // Exercise 9

Write a program that reads digits and composes them into integers. For example 123 is read as the characters 1, 2 and 3. The program should output "123 is 1 hundred and 2 tens and 3 ones". The number should be output as an int value. Handle numbers with one, two, three or four digits.

Hint: To get the integer value 5 from the character '5' subtract '0', that is '5'-'0'==5.

#include "stdafx.h"
#include <vector>
#include <string>
void pause();
void getNumbers();
void printNumbers();
using namespace std;
vector <int> digits;
char er = 'n'; //for error checking

int main()
{
 //get the numbers and convert them to an int from string
 getNumbers();

 //print the numbers out
 printNumbers();


 //ask for letter to quit the program
 pause();

 return 0;
}


void getNumbers()
{
 er = 'n';
 cout << "Please enter a number with up to 4 digits: ";
 string x;
 cin >> x; 

 //error checking
 for (int i = 0; i < x.size(); ++i)
 {
  for (char n = 'a'; n < 'z'; ++n)
  {
   while (x[i] == n)
   {
    er = 'y';
    cout << "That is not a number. Sorry.\n";
    return;
   }  
  }

  int num = x[i] - '0'; //converts letter to int
  digits.push_back(num); //pushes back into int vector
 }
}

void printNumbers()
{
 //continue to get input while er is equal to y
 while (er == 'y')
  getNumbers();

 for (int i = 0; i < digits.size(); ++i)
  cout << digits[i];

 cout << " is ";

 if (digits.size() == 4)
 {
  if (digits[0] == 1)
   cout << digits[0] << " thousand and ";
  else
   cout << digits[0] << " thousands and ";

  if (digits[1] == 1)
   cout << digits[1] << " hundred and ";
  else
   cout << digits[1] << " hundreds and ";

  if (digits[2] == 1)
   cout << digits[2] << " ten and ";
  else
   cout << digits[2] << " tens and ";

  cout << digits[3] << " ones.\n";
 }


 if (digits.size() == 3)
 {
  if (digits[0] == 1)
   cout << digits[0] << " hundred and ";
  else
   cout << digits[0] << " hundreds and ";

  if (digits[1] == 1)
   cout << digits[1] << " ten and ";
  else
   cout << digits[1] << " tens and ";

  cout << digits[2] << " ones.\n";
 }


 if (digits.size() == 2)
 {
  if (digits[0] == 1)
   cout << digits[0] << " ten and ";
  else
   cout << digits[0] << " tens and ";
  cout << digits[1] << " ones.\n";
 }

 if (digits.size() == 1)
 {
  cout << digits[0] << " ones.\n";
 }

}

void pause()
{
 cout << "\n\nPlease enter a letter: ";
 char key;
 cin >> key;
}

I'm sure there must be a much easier way to print the digits grammatically however I decided to just do this by brute force because this small program doesn't really take up any memory by doing it this way, nor does it slow it down. 

At first when I read this question I was like "what on earth does he want me to do now?" I didn't know if he wanted us to write into a char but then a char can't hold more than single character, so I thought about a vector of chars and pushing them back but that would require at least 5 different chars to push back. So I went with a string and I actually learnt something very useful today.

So string has similar functions as vector, I knew that I could get the size of it by using .size after the variable to return how many characters had been inputted. However on a whim I decided to see what would happen if I took away '0' from the character within the string, as suggested by Bjarne in the book. And it worked, it returned a number which I applied to a interger called num and then pushed that into a vector so printNumbers() had them all in one place.

Also, as a little extra this includes error checking. This doesn't allow any letters and will only allow numbers. I did this by comparing whatever the current character of x was to the alphabet using a for loop. For example, if the string x was equal to k then k would be compared to each letter of the alphabet and if it was equal to one then it returns to main and executes the next function. However the char 'er' has been set to 'y' so it will keep calling getNumbers() until er is equal to 'n'. It took me a while to get this error check working, so I'm pretty proud it does.