Orientation

  • Instructor
  • Course
  • Technical and Administrative

Introduction to Jason

About Your Instructor:

  • Jason Hemann
  • Doctorate in Computer Science, Indiana University
  • Concentration in Logic
  • Philosophy undergraduate
  • Dance and run and talk software and how it helps people
  • More at recent news article!

What is this class about, and why?

  • Why? from 10,000 ft.
  • Where do we start, and where are we going?
  • Show you some amazing stuff.
  • Give you opportunities to do some pretty awesome stuff
  • “Learn by doing”
  • Implementations and applications

Technical and Administrative

Are you with us?

  • Are you enrolled?
  • Can you see yourself in Canvas (Combined section)?
  • Can you see yourself in Piazza?

I’m not going to go through administrativa. You should!

  • Course Website
  • Full Course Schedule
  • Syllabus
  • Resources
  • (Optional) Textbooks and notes
  • Office hours
  • Piazza
  • Plan

Delta from previous years/semesters

  • “Choose your own” v. “#langs” v. Haskell v. “#lang racket”
  • late work
  • breadth vs. depth
  • continuations, control flow
  • laptops

How to succeed in this class

  1. Come to class
  2. Take vigorous notes.
  3. No laptops
  4. Do not re-write when I re-write.
    1. Instead, write down deltas-program xformations
  5. Revisit these notes to “replay” the events of lecture
    1. Use this replay to help you decipher and cement concepts in your head
    2. Working through in this level of detail will force you to grapple

If you have not already …

Download and (re-)install DrRacket

Go to https://download.racket-lang.org/, and you can download and install Racket and the DrRacket IDE for your platform. If you have used DrRacket in a previous course, you should upgrade to the latest version.

We will go ahead and install a handful of additional plugins. There are for right now a couple of different tweaks and toggles we can hit.

Via the package manager (on OSX File>Package manager) , install faster-minikanren.

We will use these at the appropriate time.

All the Racket you need to know

cons, car, and cdr.

;; (cons (car (cons α β)) (cdr (cons α β)))
;; =
;; (cons α β)

Important to write these style of programs

– As or more important than it is that you write them

We’ll do several examples.

length

count8

(define (count8 ls)
  (cond
    ((null? ls) 0)
    ((eqv? (car ls) 8) (add1 (count8 (cdr ls))))
    (else (count8 (cdr ls)))))

(define (count8* ls)
  (cond
    ((null? ls) 0)
    ;; this is our test for listitude 
    ;; we have a list, and it's car is a list
    ((pair? (car ls)) (+ (count8* (car ls)) (count8* (cdr ls))))
    ((eqv? (car ls) 8) (add1 (count8* (cdr ls))))
    (else (count8* (cdr ls)))))

(count8* '(4 (8 (5 (((8)) 7))) (3 8)))
3

rember8

;; '(4  8 5 8 7 3 8) => '(4  5 7 3) 
;;    '(8 5 8 7 3 8) =>    '(5 7 3)

(define (rember8 ls)
  (cond
    ((null? ls) '())
    ((eqv? (car ls) 8) (rember8 (cdr ls)))
    (else (cons (car ls) (rember8 (cdr ls))))))

rember8*

(define (rember8* ls)
  (cond
    ((null? ls) '())
    ((pair? (car ls)) (cons (rember8* (car ls)) (rember8* (cdr ls))))
    ((eqv? (car ls) 8) (rember8* (cdr ls)))
    (else (cons (car ls) (rember8* (cdr ls))))))

(rember8* '(4 (8 (5 (((8)) 7))) (3 8)))

Arithmetic examples, if we get there.

Updated: