npm run pull npm start

Transcription

1 1. Open Visual Studio Code 2. At the top click on View->Integrated Terminal (if not already open) 3. In the terminal, first run: npm run pull 4. After this finishes run: npm start Logical Operators Lecture 08 Mind of Logic

2 Announcements Problem Set 2 releasing tomorrow Quiz 2 Grades posted Regrade requests open More practice problems posted Released every week at Thurs tutoring session

3 Announcements Problem Set 2 releasing tomorrow Quiz 2 Grades posted Regrade requests open Videos link now live! Another great source of review

4 Polleverywhere.com/compunc

5 Polleverywhere.com/compunc

6 Polleverywhere.com/compunc

7 if-then-else Statements Notice, like the if-then statement, the then block runs only when the test condition is true Unlike the if-then statement, the else block runs only when the test condition is false After either the then-block or else-block complete, they both continue to the same next step if test then else true false

8 How do we form compound logical statements? IF UNC has a football game AND it is a home game, THEN I'll go watch. IF it is raining OR it is cold, THEN I'll grab my jacket. IF it is NOT a COMP110 assignment, THEN I will procrastinate.

9 The AND operator is && The double ampersand && is a boolean operator <boolean a> && <boolean b> AND truth table true false true true false false false false boolean value If both expressions connected by the && symbol are true, then the resulting boolean will be true. Otherwise it will be false. You read a truth table like a multiplication table. Start with a finger on one column label and one row label, per each side of the operator, and trace your way in.

10 The OR operator is The double vertical bar is a boolean operator <boolean a> <boolean b> OR truth table true false true true true false true false boolean value If either expression connected by the symbol is true, then the resulting boolean will be true. Otherwise it will be false. You read a truth table like a multiplication table. Start with a finger on one column label and one row label, per each side of the operator, and trace your way in.

11 The NOT operator is! The exclamation point is a unary boolean operator.!<boolean a> NOT truth table true false not false true boolean value The expression following the NOT operator will evaluate to the opposite boolean value. True becomes false and false becomes true.

12 Logical Operator Reference && AND OR! NOT Expression Is Expression Is Expression Is true && true true true true true!true false true && false false true false true!false true false && true false false true true false && false false false false false It is worth committing these to memory. Every programming language (including Excel) shares the same notion of these logical operations.

13 Order of Operations You can make arbitrarily complex expressions inside an if block if ((x!== y && x > 4) y = 5) Order of operations still applies (parenthesis first) Logical operators evaluated last

14 polleverywhere.com/compunc Logical Operator Practice What values for x and y would cause this to print false? let x: number = await promptnumber( x ): let y: number = await promptnumber( y ): let q1: boolean = x > 10 y < 6; print(q1);

15 polleverywhere.com/compunc Logical Operator Practice What values for x and y would cause this to print true? let x: number = await promptnumber( x ): let y: number = await promptnumber( y ): let q2: boolean = x > 2 && y < 4; print(q2);

16 polleverywhere.com/compunc Logical Operator Practice What values for x and y would cause this to print true? let x: number = await promptnumber( x ): let y: number = await promptnumber( y ): let q3: boolean = (x > 5 y < 10) && y >= 10; print(q3);

17 polleverywhere.com/compunc Logical Operator Practice What values for x and y would cause this to print true? let x: number = await promptnumber( x ): let y: number = await promptnumber( y ): let q4: boolean = (!true && x < 3) && (y < 6 false); print(q4);

18 Multiple if blocks Each if block is associated with 0 or 1 else blocks An else is always associated with the if that immediately precedes it at the same block level let day: string = await promptstring( What day is it? ); if (day === Monday ) { print( COMP101 is today!!! ); } else { if (day === Friday ) { print( Quiz day ); } else { print( No COMP101 today! ); } } if (day === Saturday ) { print( Time to procrastinate ); }

19 Hands-on Dumb Siri 1. Open 00-dumb-siri-app.ts if (<condition>) { // then } else { // else } 2. If it is cold and raining, tell the user they need a jacket and an umbrella 3. If it is only cold, tell the user to wear a jacket 4. If it is only raining tell the user to bring an umbrella 5. If it is neither cold nor raining tell the user the weather is nice Check-in on PollEv.com/compunc once your dumb siri is complete!

20 if (iscold === true && israining === true) { print("you need a jacket and an umbrella"); } if (iscold === true) { print("you need to wear a jacket"); } if (israining === true) { print("you need to bring an umbrella"); } if (israining === false && iscold === false) { print("the weather is nice!"); }