Hailperin, Chapter 1

Slides, Intro Course.

Slide, Demo Scheme.

> 13
> -4
> 2/3
> .666
> 4/6
> 2+3 error
> (+ 2 3)
> (sqrt 16)
> sqrt
> +
> 2+3i
> (sqrt 2+3i)
> -7
> (- 7)
> (- -7)

various nested expressions

> (define myPi 3.1415962)
> myPi
> (/ 22 7)
> (/ 22 7.)
> (define myPi (/ 22 7.))
> myPi

> sqrt
> (sqrt 25)
> (square 5) error
> (* 5 5)
> (lambda (x) (* x x))
> ((lambda (x) (* x x)) 5)

Slide, Lambda expression, Function
Slide, Lambda expression, Parameter list

Class exercise: Write a function that returns the area of a circle of radius r, then apply it to a circle with radius 13.

Naming functions

Class exercise: Write a function that names the function square.
> (define square (lambda (x) (* x x)))
> (square 5)

Class exercise: Write a function that names the function area.

> (define area (lambda (r) (* myPi (square r))))
> (area 13)

Demo defining in the editor pane with the Run button.

> (< 2 3)
> (> 2 3)
> #t
> #f
> (if #t 5 7)
> (if #f 5 7)
> (abs -7)

Class exercise: Write a function myabs that returns the absolute value of a number.

(define myabs
  (lambda (x)
    (if (< x 0) (- x) x)))

Quilting - see Setup for Scheme
Note the following two steps.
1. Install concabs.plt. Only required once.
2. Copy and paste quilt.txt into editor window. Required each time.

Demo
> rcross-bb
> corner-bb
> test-bb
> nova-bb

> (stack rcross-bb corner-bb)
> test-bb
> (quarter-turn-right test-bb)

Predict
> (quarter-turn-right (stack test-bb test-bb))
> (stack (quarter-turn-right test-bb) test-bb)
> (stack (quarter-turn-right test-bb) test-bb)

Class exercise: Create the pattern from the slide: Quilt pattern

> (stack (quarter-turn-right (stack rcross-bb rcross-bb))
         (quarter-turn-right (stack rcross-bb rcross-bb)))