UNB/ CS/ David Bremner/ teaching/ cs2613/ labs/ Lab 3

Before the lab

Reading

Git Practice: Working with multiple git repos

Time
15-30 minutes
Activity
Individual work, outside scheduled lab time.

Cloning

  1. Open a terminal.

  2. Make a directory lab2-scratch somewhere outside the cs2613 git repository you created earlier.

  3. Now move to the lab2-scratch directory, and make a clone of the central repo.

     $ git clone -b main https://$username@vcs.cs.unb.ca/git/cs2613-$username cs2613-clone

    This creates a new directory "cs2613-clone" containing a clone of your repository. Notice that in general this is a good way of checking that your work is properly submitted. The TA and Prof will do exactly this cloning step in order to mark your work. The clone is on an equal footing with the original project, possessing its own copy of the original project’s history.

Sharing changes with a central repo

Optional, but useful if you plan to run git on your own computer

  1. Open a terminal

  2. Navigate to the ~/lab2-scratch/cs2613-clone/journal directory.

  3. create a new blog entry, and commit it.

  4. Push your changes back to the central repository.

     $ git push origin main

  5. Change directory to your original directory ~/cs2613. Bring in the changes you made

     $ git pull origin main

This merges the changes from the central copy of "main" branch into the current branch. If you made other changes in the meantime, then you may need to manually fix any conflicts.

The "pull" command thus performs two operations: it fetches changes from a remote branch, then merges them into the current branch.

Questions

Here are some questions we will be discussing at the beginning of L03.

Git next steps

Congratulations, you now know enough git to finish this course.

There is lots more to learn, particularly about branching and collaboration. If you want to get a big(ger) picture view, a good place to start is Git Concepts Simplified.

Git Questions

Time
10 Minutes
Activity
Group discussion

Some questions from before:

Setup

The DrRacket stepper

Time
20 min
Activity
Individual work

Unit testing is an important part of programming, and has inspired something called test driven development.

This part is based on an example from RackUnit QuickStart. - copy arith.rkt, save it as ~/cs2613/labs/L03/arith.rkt and commit it.

Semantics

Time
20 min
Activity
Small Groups
Summary
new evaluation rules for and and or

As you read in FICS unit 3, we can understand evaluation ("running") of Racket programs as a sequence of "reductions" or "substitutions". These rules are similar to the reduction steps in the DrRacket stepper.

The stepper uses the following rules for and and or (notice that these rules enforce short circuit evaluation)

(and true exp2 ...) => (and exp2 ...)
(and false exp2 ...) => false
(or true exp2 ...) => true
(or false exp2 ...) => (or exp2 ...)
(and) => true
(or) => false

Following Exercise 7, write a new set of rules that requires at least two arguments for and and or. The rules are for human consumption; you can write them as comments in DrRacket. You can write "exp1 exp2 ..." to mean at least 2 expressions.

Discuss your answers with a your group, and try a couple evaluation small examples by hand using your rules.

Test Coverage

Time
25 min
Activity
Individual work

If you have extra time

Before Next Lab

Reading for next lab

On your own

Time
20 min
Activity
Independent research

See if you can come up with answers to the following questions for next time.