16-07mar15loops

• Notes
• 2

This preview shows page 2 out of 2 pages.

x = sum of 1..10 Put your answer here Suppose this assertion is true: no value in h..k divides x Under what extra condition is this one true? no value in 2..n–1 divides x Put your answer here 11 Understanding assertions This is an assertion about v and k. It is true because chars of v[0..3] are greater than ‘C’ and chars of v[6..8] are ‘Z’s. 0 1 2 3 4 5 6 7 8 X Y Z X A C Z Z Z v This is a list of Characters v C ? all Z’s k 6 0 3 k 8 v C ? all Z’s k 5 0 3 k 8 v C all Z’s k 6 0 k 8 v W A C all Z’s k 4 0 k 8 Indicate whether each of these 3 assertions is true or false. 12 We add the postcondition and also show where the invariant must be true: initialization; // invariant: P while ( B ) { // { P and B} repetend // { P } } // { P } // { Result R } The four loopy questions Suppose we have this while loop, with initialization: initialization; while ( B ) { repetend } Second box helps us develop four loopy questions for developing or understanding a loop: 1. How does loop start? Initialization must truthify inv P. 2. When does loop stop? At end, P and !B are true, and these must imply R. Find !B that satisfies P && !B => R. 3. Make progress toward termination? Put something in repetend to ensure this. 4. How to keep invariant true? Put something in repetend to ensure this.
You've reached the end of this preview.
• Spring '07
• DAVIDGRIES

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern