CS 380 2025spring ibarland

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structs intro
incl. immutability (using racket)

2019-Feb snow day!: In class Feb-06, we covered the first video below ("structs-intro-part1"), plus all but the last 2m41s of the next (part2).
For Feb-11 (or at least before Feb-13 and hw04a):

• watch, starting from 19m00s, the last few minutes of video: part 2: template for structs (21m41s),
• and then (at least) the first 13m00s of video: part 3: functions returning struct (19m15s) (if you a further worked-out example of the the design recipe applied to another function-for-immutable-structs, you can continue watching after 13m00s), and
• finally, watch video: Java records for structs intro (part 4). (24m26s)
• Optional: Using Java w/ class instead of record is both painful and has a couple subtleties.

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• book.rkt (before videos)
• Structs in racket: defining; constructors & accessors; examples of the data. video: structs intro (part 1) (14m25s)
  
  
• Functions processing structs; the template for structs. video: structs intro (part 2) (21m41s)
  
  
• Functions returning structs; new structs rather than mutating. video: structs intro (part 3) (19m15s)
  
  
• book.rkt (at end of videos)
• The design recipe isn't racket-specific, of course:
  Here is Book using Java (and its records): video: Java records for structs intro (part 4) (24m26s)
  
  Source code files: just the record-declaration, with a couple methods, and all methods & tests,
  as well as in Scala.
• Optional: Although it's not part of the gist of the course, doing the same thing in Java without records takes more work.
  What you really need to do, to do handle (immutable) classes correctly (not always fully-obvious):
  • boring: video: boilerplate-java-1-constructor-toString (20m16s)
  • a subtlety: video: how to override equals (19m15s), and
  • Remember: If you override equals, you most also override hashCode: video: how to override hashCode (14m35s).

opening notes in .rkt files: Many of the lecture-notes links are .rkt files (not .html). You should (a) download the file (say, via right-click or save-as), (b) start DrRacket, and then (c) choose File &goto; Open… them. Do not copy-paste into an empty DrRacket window — the language-preference won't be set correctly, and the initial lines may be goofed up.

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