#include <iostream>
#include <cmath>

using namespace std;

// prototype for my functions
void funcMenu();
double quadratic (double a, double b, double c);
bool isEven (int num);
void isItPosNegOrZero(double num);
double absoluteValue(double num);
void printChar(char c1);

int main() {

    //This is the equivalent of our start button to engage with the program
    int program;
    cout << "Type 1 to enter program and 0 to exit: ";
    cin >> program;

    int choice;
    //this if statement allows us to enter the program
    if (program == 1)
    {
        //this do while statement executes the menu and the choice selection
        do
        {
            funcMenu();
            cin >> choice;

            // this switch statement allows us to pick which feature of the program we desire to engage, from quadratic equation, determining if it's even, whether its negative or positive or 0, the absolute value and the change of character from upper to lower and vice versa.
            switch (choice) {

                case 1:
                    double num1, num2, num3;
                    cout << "Enter three consecutive real numbers each followed by a space: ";
                    cin >> num1 >> num2 >> num3;
                    double result1;
                    result1 = quadratic(num1, num2, num3);
                    cout << result1 << endl;
                    break;

                case 2:
                    int num4;
                    cout << "Enter an integer to determine if it's even: ";
                    cin >> num4;
                    bool result2;
                    result2 = isEven(num4);
                    cout << result2 << endl;
                    break;

                case 3:
                    double num5;
                    cout << "Enter an integer to determine whether it's positive or negative: ";
                    cin >> num5;
                    isItPosNegOrZero(num5);
                    cout << endl;
                    break;

                case 4:
                    double num6;
                    cout << "Enter a positive or negative integer to determine its absolute value: ";
                    cin >> num6;
                    double result3;
                    result3 = absoluteValue(num6);
                    cout << result3 << endl;
                    break;

                case 5:
                    char character;
                    cout << "Enter a character: ";
                    cin >> character;
                    printChar(character);
                    cout << endl;
            }
        }
        while (choice < 1 || choice > 6);
    }
    else
    {
        cout << "Please come again whenever you need!\n";
    }
    return 0;
}
//here are our functions for the program, including the menu and the functions that perform the operations selected from the menu itself
void funcMenu ()
{
    //don't need all these cout's, evidently from textbook, but it makes it feel uniform
    cout << "\n\t\t Menu of Functions\n\n";
    cout << "1. Quadratic Formula\n";
    cout << "2. Is it Even or Odd\n";
    cout << "3. Postive Negative or Zero\n";
    cout << "4. The Absolute Value\n";
    cout << "5. Character Case Changer\n";
    cout << "6. Exit\n\n";
    cout << "Enter your choice: ";
}
// Here are our functions which perform the neccesary, well, functions to determine our objectives
double quadratic (double a, double b, double c)
{
    double results;

    if (a == 0)
    {
        cout << "no solution for a=0 ";
        return 0;

    }
    else if (pow(b,2) - 4*a*c < 0)
    {
        cout << " no real solutions ";
        return 0;
    }
    else
    {
        results = (-b + sqrt(pow(b,2) - 4*a*c))/(2*a);
        return results;
    }
}

bool isEven (int num)
{
    bool testValue;
    if (num%2 == 0)
    {
        testValue = true;
    }
    else
    {
        testValue = false;
    }
    return testValue;
}

void isItPosNegOrZero(double num)
{
    if (num == 0)
    {
        cout << 0 << endl;
    }
    else if(num > 0)
    {
        cout << '+' << endl;
    }
    else
    {
        cout << '-' << endl;
    }
    return;
}

double absoluteValue(double num)
{
    double num1;

    if (num > 1)
    {
        num1 = num;
    }
    else
    {
        num1 = num * -1;
    }
    return num1;
}

void printChar(char c1)
{
    char letter;
    if(c1 >= 65 && c1 <= 90)
    {
        letter = c1 + 32;
        cout << letter << endl;
    }
    else if (c1 >= 97 && c1 <= 122)
    {
        letter = c1 - 32;
        cout << letter << endl;
    }
    return;
}