Lecture 02 (#1)

.github/workflows/deploy.yml

@@ -3,11 +3,13 @@
 name: Deploy VitePress site to Pages
 
 on:
- # Runs on pushes targeting the `main` branch. Change this to `master` if you're
- # using the `master` branch as the default branch.
  push:
  branches: [main]
 
+ pull_request:
+ branches:
+ - main
+
  # Allows you to run this workflow manually from the Actions tab
  workflow_dispatch:
 
@@ -54,6 +56,7 @@ jobs:
 
  # Deployment job
  deploy:
+ if: github.event.pull_request.base.ref == 'refs/heads/main'
  environment:
  name: github-pages
  url: ${{ steps.deployment.outputs.page_url }}

.vitepress/config.mts

@@ -27,7 +27,8 @@ export default defineConfig({
  text: 'Lectures',
  link: '/lectures/',
  items: [
- { text: '01: Introduction', link: '/lectures/lecture01'}
+ { text: '01: Introduction', link: '/lectures/lecture01'},
+ { text: '02: Lists & Trees', link: '/lectures/lecture02'},
  ]
  },
 

labs/lab01.md

@@ -4,19 +4,17 @@ outline: deep
 
 # Lab 1: Introduction to Racket
 
-This lab aims to familiarize the students with the IDE we will use for Racket and help them write
-simple programs.
+In this lab you will familiarize yourself with the IDE we will use to write Racket programs.
 
 ## Dr. Racket IDE
 
-The IDE can be downloaded for free for Linux, Windows, and MAC from:
-https://racket-lang.org/
+The IDE can be downloaded for free for Linux, Windows, and MAC from: https://racket-lang.org/
 
-The students can use the one installed in the lab computers. The teacher may help the students (to a
-reasonable degree) to get the IDE running on students’ laptops.
+You can use the one installed in the lab computers or install it on your own laptop. Don't hesitate
+to ask for help!
 
-Get familiar with the definition window and REPL in DrRacket. The documentation of implemented
-functions is accessible via Help Desk in the menu.
+To get familiar with the definition window and REPL in DrRacket you can:
+* Read documentation of implemented functions which is accessible via **Help Desk** in the menu.
 
 DrRacket allows writing programs in several languages. We focus on Racket, so your first line in the
 code should be:
@@ -25,7 +23,7 @@ code should be:
 ```
 
 ## Exercises - Racket basics
-Start interaction in REPL. Racket uses prefix notation for all functions. Let students compute
+Start interaction in REPL. Racket uses prefix notation for all functions. Try and compute a
 simple formulas, e.g., $2+3/5$.
 
 ### Exercise 1
@@ -80,7 +78,7 @@ consisting of a sequence of consecutive characters starting with `fst`, ending w
 following the order in the ASCII table.
 For example `(consecutive-chars #\A #\D) => "ABCD"` or `(consecutive-chars #\z #\u) => "zyxwvu"`.
 For converting characters into positions in the ASCII table, use functions
-`<nowiki>char->integer</nowiki>` and `<nowiki>integer->char</nowiki>`. To convert a character into a
+`char->integer` and `integer->char`. To convert a character into a
 string, apply the function `string`.
 
 ::: details Solution
@@ -98,9 +96,11 @@ string, apply the function `string`.
  (iter (+ k step)
  (string-append acc (integer->string k)))))
  (iter first-index ""))
+```
 
-; alternatively:
-#|
+Alternatively, and maybe slightly more elegantly, you can define two helper functions `char+1` and
+`char-1` and use an accumulator:
+```scheme
 (define (char+1 c) (integer->char (add1 (char->integer c))))
 (define (char-1 c) (integer->char (sub1 (char->integer c))))
 
@@ -111,8 +111,6 @@ string, apply the function `string`.
  (consecutive-chars (char+1 fst) lst (string-append acc (string fst)))]
  [(char>? fst lst)
  (consecutive-chars (char-1 fst) lst (string-append acc (string fst)))]))
-|#
-
 ```
 :::
 

lectures/index.md

@@ -7,14 +7,17 @@ due to other obligations.
 ## [Lecture 01](lecture01): Introduction
 Discusses the key ideas behind functional programming. It further
 introduces the programming language [Racket](https://racket-lang.org/).
+
 [Slides](https://drive.google.com/file/d/1e1aw5Mf5qts0DxLJFDZUWDbGlwI0hdeM/view?usp=drive_link).
 [Log](https://drive.google.com/file/d/1I3uoTART5UmWsWLRR_bYuNrzolTl2cO5/view?usp=share_link).
 
+## [Lecture 02](lecture02): Lists & Trees
+Focuses on Racket lists and trees. Further, it introduces the unit testing library
+[Rackunit](https://docs.racket-lang.org/rackunit/index.html).
 
-<!--
-2. [Lecture 2](lecture02) focuses on Racket lists and trees. Further, it introduces the unit testing
- library [Rackunit](https://docs.racket-lang.org/rackunit/index.html).
+[Slides](https://drive.google.com/file/d/1PalOH5j2BvNzBtmAVe4v9dZosf_B-jKQ/view?usp=drive_link).
 
+<!--
 3. [Lecture 3](lecture03) deals with higher-order functions, function closures and Racket structures.
 
 4. [Lecture 4](lecture04) introduces pattern matching, and explains how to implement lazy

lectures/lecture01.md

@@ -761,6 +761,9 @@ grows exponentially in the recursion depth. So one should be careful when design
 function. Still, tree-recursive functions are natural and powerful when dealing with tree-structured
 data like algebraic expressions or tree-generative processes like fractals.
 
+
+#### Drawing trees
+
 As an example of the tree recursion, consider a tree-like fractal of a given size $n$ and direction
 $d$ in degrees generated according to the following rules:
 
@@ -778,9 +781,13 @@ recursive calls.
 
 ![Recursive generation of a tree-like fractal](../img/fractal.svg){ style="width: 100%; margin: auto;" }
 
-Now, let us see how to program this procedure in Racket. First, we need a drawing library if we want to draw something. Racket contains a simple library called 
+Now, let us see how to program this procedure in Racket. First, we need a drawing library if we want
+to draw something. Racket contains a simple library called 
 [value-turtles](https://docs.racket-lang.org/turtles/Value_Turtles.html). 
-Functions in this library update an image containing "a turtle" with a position and direction. For example, we can draw a line of a given length in the turtle's direction or turn the turtle by an angle. Further, we can extract the turtle's state from a given image and restore the state later on. The code of the program is below.
+Functions in this library update an image containing "a turtle" with a position and direction. For
+example, we can draw a line of a given length in the turtle's direction or turn the turtle by an
+angle. Further, we can extract the turtle's state from a given image and restore the state later on.
+The code of the program is below.
 
 ```scheme:line-numbers
 #lang racket