Decision Structure - 2 ISYS 350

Complex Condition with Logical Operators The logical AND operator (&&) and the logical OR operator (||) allow you to connect multiple Boolean expressions to create a compound expression The logical NOT operator (!) reverses the truth of a Boolean expression OperatorMeaningDescription &&ANDBoth subexpression must be true for the compound expression to be true ||OROne or both subexpression must be true for the compound expression to be true !NOTIt negates (reverses) the value to its opposite one. ExpressionMeaning x >y && a < bIs x greater than y AND is a less than b? x == y || x == zIs x equal to y OR is x equal to z? ! (x > y)Is the expression x > y NOT true?

Logical Operators: &&, ||, ! && Cond1Cond2Cond1 && Cond2T TF FTF || Cond1Cond2Cond1 || Cond2T TF FTF ! Cond! Cond T F

Examples Write a complex condition for: 12 <= Age <= 65 Use a complex condition to describe age not between 12 and 65. X <= 15 is equivalent to: X<15 AND X =15? (T/F)

More Complex Conditions University admission rules: Applicants will be admitted if meet one of the following rules: – 1. Income >= 100,000 – 2. GPA > 2.5 AND SAT > 900 An applicant’s Income is 150,000, GPA is 2.9 and SAT is 800. Admitted? – Income >= 100,000 OR GPA > 2.5 AND SAT >900 How to evaluate this complex condition? – AND has higher priority

Scholarship: Business students with GPA at least 3.2 and major in Accounting or CIS qualified to apply: – 1. GPA >= 3.2 – 2. Major in Accounting OR CIS Is a CIS student with GPA = 2.0 qualified? – GPA >= 3.2 AND Major = “Acct” OR Major = “CIS” Is this complex condition correct? – Parenthesis, ( )

NOT Set 1: Young: Age < 30 Set 2: Rich: Income >= 100,000 YoungRich

Young: Age private void button1_Click(object sender, EventArgs e) { double Age, Income; Age = double.Parse(textBox1.Text); Income = double.Parse(textBox2.Text); if (Age ) MessageBox.Show("You are young and rich"); else MessageBox.Show("You are not young or not rich"); }

Boolean (bool) Variables and Flags You can store the values true or false in bool variables, which are commonly used as flags A flag is a variable that signals when some condition exists in the program – False – indicates the condition does not exist – True – indicates the condition exists Boolean good; // bool good; if (mydate.Year == 2011) { good = true; } else { good = false; } MessageBox.Show(good.ToString());

Using Boolean Variables and && private void button1_Click(object sender, EventArgs e) { bool Young=false, Rich=false; double Age, Income; Age = double.Parse(textBox1.Text); Income = double.Parse(textBox2.Text); if (Age < 30) Young = true; if (Income > ) Rich = true; if (Young && Rich) MessageBox.Show("You are young and rich"); else MessageBox.Show("You are not young OR not rich"); }

Using Boolean Variables and || private void button1_Click(object sender, EventArgs e) { bool Young=false, Rich=false; double Age, Income; Age = double.Parse(textBox1.Text); Income = double.Parse(textBox2.Text); if (Age < 30) Young = true; if (Income > ) Rich = true; if (Young || Rich) MessageBox.Show("You are young OR rich"); else MessageBox.Show("You are not young and not rich"); }

The if-else-if Statement Rules to determine letter grade Avg>=90 A 80<=Avg<90 B 70<=Avg<80C 60<=Avg<70D Avg<60F

Compare the two programs if (grade < 60) { MessageBox.Show("F"); } else if (grade < 70) { MessageBox.Show("D"); } else if (grade < 80) { MessageBox.Show("C"); } else if (grade < 90) { MessageBox.Show("B"); } else { MessageBox.Show("A"); } if (grade < 60) { MessageBox.Show("F"); } if (grade >=60 && grade < 70) { MessageBox.Show("D"); } if (grade >= 70 && grade < 80) { MessageBox.Show("C"); } if (grade >= 80 && grade < 90) { MessageBox.Show("B"); } if (grade >=90 ) { MessageBox.Show("A"); }

Tax Rate Schedule Rules to determine tax rate: – Taxable Income < =3000 no tax – 3000 < taxable income <= % tax – 10000<Taxable income <= % tax – Taxable income> % double taxableIncome, taxRate, tax; taxableIncome = double.Parse(textBox1.Text); if (taxableIncome <= 3000) { taxRate = 0; } else if (taxableIncome<=10000) { taxRate=.05; } else if (taxableIncome <= 50000) { taxRate =.15; } else { taxRate =.25; } tax = taxableIncome * taxRate; textBox2.Text = tax.ToString("C");

Data Entered in Textbox1 Must Be between 10 and 30 private void textBox1_Validating(object sender, CancelEventArgs e) { double enteredData; enteredData = double.Parse(textBox1.Text); if (enteredData 30) { MessageBox.Show("Pls enter a number between 10 and 30"); e.Cancel=true; }

Working with DateTime Get current date: – DateTime thisDate=DateTime.Today; Get current date and time: – DateTime thisDate=DateTime.Now; Calculate # of days between two dates: – myDate = DateTime.Parse(textBox1.Text); – DaysBetween = thisDate.Subtract(myDate).Days;

Compute Age Given DOB: Age =65, Old DateTime myDate, thisDate=DateTime.Today; double Age; myDate = DateTime.Parse(textBox1.Text); Age = (thisDate.Subtract(myDate).Days / 365); MessageBox.Show(Age.ToString()); If (Age<30) MessageBox.Show(“Young”); elseif (Age<65) MessageBox.Show(“Middle”); else MessageBox.Show(“Old”);

Date Comparison DateTime thisDate, currentDate = DateTime.Today; thisDate = DateTime.Parse(textBox1.Text); if (currentDate>thisDate) MessageBox.Show("after"); else MessageBox.Show("before");

Using TimeSpan to calculate the number of days between two dates TimeSpan class: TimeSpan represents a length of time. Define a TimeSpan variable: TimeSpan ts; We may use a TimeSpan class variable to represent the length between two dates: ts = laterDate-earlierDate;

Code Example DateTime earlierDate, laterDate; double daysBetween; TimeSpan ts; earlierDate = DateTime.Parse(textBox1.Text); laterDate = DateTime.Parse(textBox2.Text); ts = laterDate-earlierDate; daysBetween = ts.Days; MessageBox.Show("There are " + daysBetween.ToString() + " days between " + earlierDate.ToShortDateString() + " and " + laterDate.ToShortDateString()); Note: Pay attention to how we create the output string.