/* This program demonstrates
 * 1. The multiple if statemet
 * 2. The swicth statement
 * 3. Fall through and character inputs for a switch statement
 *
 * Multiple if statement
 * A simple if else statement is only capable of implementing two
 * situations. If that condition were true, the if block is executed;
 * otherwise, the else block is executed.
 * If we have more than 2 situations, we can attach another if...else
 * statement to the else part. We can keep doing this to account for as
 * many situations as we want, as long as each situation can be adequately
 * represented by a condition. The final else (optional) can take care of
 * the "none of the above" case.
 * else and if should be separate, please don't write "elseif"
 * The multiple if..else statement is greedy. It will take the first branch
 * whose condition is "true", and ignore all others.
 *
 * The switch statement
 * If we have a situation where the following conditions are satisfied, we
 * can express the multiple if statement as a switch statement.
 * 1. All the conditions in the if statement should involve the same variable
 * 2. The variable should be an integer type (char, short, int or long)
 * 3. All the comparisons should be equality comparisons (==)
 * 4. The comparisons should involve the variable and a constant/literal
 * The syntax for the switch statement is given below.
 * switch, case, break and default are all keywords/reserved words.
 * We "switch" the variable involved.
 * Each of the constants/literals we compare the variable to would get their own "case"
 * The colon after the case label is not optional.
 * All the contents of the if block for that constant/literal are placed after the :
 * Once we are done with a particular case, be "break" out of the switch statement
 * Within the switch statement, the order of the cases don't matter.
 * Except for the default (none of the above) case, which should always be at the very end.
 * If we don't break out of the switch statement at the end of the case, control will
 * "fall through" and execute the statements for the following cases until it sees a
 * break statement or reaches the end of the switch, whichever is earlier.
 * To avoid this, please include a break statement after you are done with each case.
 */

#include<iostream>
using namespace std;
int main()
{
    double cp,pe,ds,exam, hw;   //already weighted grades for class participation, practice
    // exercises, discussion sessions, exams and hw assignments
    cout<<"Enter the grades: ";
    cin>>cp>>pe>>ds>>exam>>hw;

    double grade = cp + ds + pe + exam +hw + 2; // 2 points for 1st day quiz, help sessions

    char letterGrade;

    // This is a multiple if statement, also called an if-else ladder

    if (grade >= 90)
    {
        letterGrade = 'A';
    }
    else if (grade <90 && grade >= 80)
    {
        letterGrade = 'B';
    }
    else if (grade <80 && grade >=70)
        letterGrade = 'C';
    else if (grade < 70 && grade >= 60)
        letterGrade = 'D';
    else if (grade < 60)
        letterGrade = 'F';

    cout<<"Letter grade: "<<letterGrade<<endl;

    /* In the following example, we discuss a special case of the multiple if statement
   * Here, we define numbers to refer to the days of the week.
   * For example, 1 is Monday, 2 is Tuesday, and so on.
   * We read in the number from the user and then print the corresponding
   * day of the week.
   */
    int day;
    cout<<"Enter the day (number): ";
    cin>>day;
    int dayofWeek = 3;
    if (day == 1)
        cout<<"Monday";
    else if(day == 2)
        cout<<"Tuesday";
    else if(day == 5)
        cout<<"Friday";
    else if(day ==4)
        cout<<"Thursday";
    else if(day == dayofWeek)
        cout<<"Wednesday";
    else if(day==6)
        cout<<"Saturday";
    else if(day ==7)
        cout<<"Sunday";
    else cout<<"Not a valid entry";

    cout<<endl<<"Switch:"<<endl;

    /* The following switch statement has exactly the same effect as the previous multiple
     * if statement. This is just to demonstrate how to convert a multiple if statement (that
	 * satisfies the conditions for a switch) into a switch statement and vice-versa.
     * Case labels also have to be unique
	 */
    switch(day)
    {
        case 1: cout<<"Monday";
            break;
        case 2: cout<<"Tuesday";
            break;
        case 3: cout<<"Wednesday";
            break;
        case 4: cout<<"Thursday";
            break;
        case 5: cout<<"Friday";
            break;
        case 6: cout<<"Saturday";
            break;
        case 7: cout<<"Sunday";
            break;
        default: cout<<"Invalid input";
    }
    cout<<endl;
	
	/* The following example will read in a character representing a month and print the
	 * name of the month and the number of days in that month in a standard calendar year.
	 * This demonstrates how to use a char variable in a switch statement. The case labels
	 * need to be single quoted.
	 */
    char month;
    cout<<"Enter the month (letter): ";
    cin>>month;
    int daysInMonth=0;
    switch(month)
    {
        case 'F': daysInMonth=28;       // February
            break;
        case 'A':                       // April
        case 'j':                       // June
        case 'S':                       // September
        case 'N': daysInMonth=30;       // November
            break;
        case 'J':                       // January
        case 'M':                       // March
        case 'm':                       // May
        case 'U':                       // July, since both J's were taken already
        case 'a':                       // August
        case 'O':                       // October
        case 'D': daysInMonth=31;       // December
            break;
        default: cout<<"Invalid month"<<endl;
    }
    if(daysInMonth !=0)     // quick check to see if there is a valid number of days to print
        cout<<"Days in month: "<<daysInMonth<<endl;

    return 0;
}