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chapter-8.txt
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chapter-8.txt
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MIT/GNU Scheme running under OS X
Type `^C' (control-C) followed by `H' to obtain information about interrupts.
Copyright (C) 2022 Massachusetts Institute of Technology
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.
Image saved on Saturday September 2, 2023 at 2:29:59 AM
Release 12.1 || SF || CREF || LIAR/svm1 || SOS || XML || Edwin || X11 || X11-Screen || ScmUtils
;Loading "/Users/harish/.emacs.d/elpa/geiser-mit-20211204.1935/src/geiser/load.scm"...
; Loading "compile.scm"...
; Generating SCode for file: "emacs.scm" => "emacs.bin"... done
; Compiling file: "emacs.bin" => "emacs.com"... done
; Dumping "geiser-w32.pkd"... done
; Dumping "geiser-unx.pkd"... done
; ... done
; Loading "geiser-unx.pkd"... done
; Loading "emacs.com"...
; Loading "format.com"... done
; ... done
;... done
1 (user) => (+ 1 2.14)
#| 3.14 |#
2 error> (+ 1 (* 2 1.07))
#| 3.14 |#
2 error> (lambda (x) (* x x))
#|
(lambda (x)
???)
|#
2 error> (lambda (x) (* x x) 4)
#|
(lambda (x)
???)
|#
2 error> (restart 1)
;Abort!
1 (user) => (lambda (x) (* x x) 4)
#|
(lambda (x)
???)
|#
1 (user) => ((lambda (x) (* x x)) 4)
#| 16 |#
1 (user) => (define pi 3.141592653589793)
#| pi |#
1 (user) => (define square (lambda (x) (* x x)))
#| square |#
1 (user) => (* 4 pi (square 5))
#| 314.1592653589793 |#
1 (user) => (define (square x) (* x x))
#| square |#
1 (user) => (* 4 pi (square 5))
#| 314.1592653589793 |#
1 (user) => (define compose
(lambda (f g)
(lambda (x)
(f (g x)))))
#| compose |#
1 (user) => ((compose square sin) 2)
#| .826821810431806 |#
1 (user) => (square (sin 2))
#| .826821810431806 |#
1 (user) => (define (compose f g)
(lambda (x)
(f (g x))))
#| compose |#
1 (user) => (define ((compose f g) x)
(f (g x)))
#| compose |#
1 (user) => ((compose square sin) 2)
#| .826821810431806 |#
1 (user) => (define (abs x)
(cond ((< x 0) (- x))
((= x 0) x)
((> x 0) x)))
#| abs |#
1 (user) => (abs -2)
#| 2 |#
1 (user) => (define (abs x)
(if (< x 0)
(- x)
x))
#| abs |#
1 (user) => (abs -10.3)
#| 10.3 |#
1 (user) => (abs - 10.3)
;The procedure #[compound-procedure 27 abs] has been called with 2 arguments; it requires exactly 1 argument.
;To continue, call RESTART with an option number:
; (RESTART 1) => Return to read-eval-print level 1.
2 error> (restart 1)
;Abort!
1 (user) => (define (factorial n)
(if (= n 1)
1
(* n (factorial (- n 1)))))
#| factorial |#
1 (user) => (factorial 3)
#| 6 |#
1 (user) => (factorial 7)
#| 5040 |#
1 (user) => (define (f radius)
(let ((area (* 4 pi (square radius)))
(volume (* 4/3 pi (cube radius))))
(/ volume area)))
#| f |#
1 (user) => (f 3)
#| .9999999999999999 |#
1 (user) => (define (factorial n)
(let factlp ((count 1) (answer 1))
(if (> count n)
answer
(factlp (+ count 1) (* count answer)))))
#| factorial |#
1 (user) => (factorial 7)
#| 5040 |#
1 (user) => (define a-list (list 6 946 8 356 12 620))
#| a-list |#
1 (user) => a-list
#|
(6 946 8 356 12 620)
|#
1 (user) => (list-ref a-list 3)
#| 356 |#
1 (user) => (list-ref a-list 0)
#| 6 |#
1 (user) => (car a-list)
#| 6 |#
1 (user) => (cdr a-list)
#|
(946 8 356 12 620)
|#
1 (user) => (define another-list
(cons 32 (cdr a-list)))
#| another-list |#
1 (user) => another-list
#|
(32 946 8 356 12 620)
|#
1 (user) => (car (cdr another-list))
#| 946 |#
1 (user) => (car (cdr a-list))
#| 946 |#
1 (user) => (define a-vector (vector 37 63 49 21 88 56))
#| a-vector |#
1 (user) => a-vector
#|
(up 37 63 49 21 88 56)
|#
1 (user) => (vector-ref a-vector 3)
#| 21 |#
1 (user) => (vector-ref a-vector 0)
#| 37 |#
1 (user) => (vector? a-vector)
#| #t |#
1 (user) => (vector? a-list)
#| #f |#
1 (user) => (list? a-vector)
#| #f |#
1 (user) => (pair? a-list)
#| #t |#
1 (user) => (list? a-list)
#| #t |#
1 (user) => (define (sum? expression)
(and (pair? expression)
(eq? (car expression) '+)))
#| sum? |#
1 (user) => (sum? '(+ 3 a))
#| #t |#
1 (user) => (sum? '(* 3 a))
#| #f |#
1 (user) => (sum? (+ 3 1))
#| #f |#
1 (user) => (+ 3 1)
#| 4 |#
1 (user) => (define a 3)
#| a |#
1 (user) => (sum? (+ 3 a))
#| #t |#
1 (user) => (sum? (+ 3 a))
#| #f |#
1 (user) => (write-line 1 2)
;The object 2, passed as an argument to write-line, is not the correct type.
;To continue, call RESTART with an option number:
; (RESTART 1) => Return to read-eval-print level 1.
2 error> (restart 1)
;Abort!
1 (user) => (write-line (list 1 2))
(1 2)
;No return value.
1 (user) => (define (factorial n)
(let factlp ((count 1) (answer 1))
(write-line (list count answer))
(if (> count n)
answer
(factlp (+ count 1) (* count answer)))))
#| factorial |#
1 (user) => (factorial 5)
(1 1)
(2 1)
(3 2)
(4 6)
(5 24)
(6 120)
#| 120 |#
1 (user) => (define (make-counter)
(let ((count 0))
(lambda ()
(set! count (+ count 1))
count)))
#| make-counter |#
1 (user) => (define c1 (make-counter))
#| c1 |#
1 (user) => (define c2 (make-counter))
#| c2 |#
1 (user) => (c1)
#| 1 |#
1 (user) => (c1)
#| 2 |#
1 (user) => (c1)
#| 3 |#
1 (user) => (c2)
#| 1 |#
1 (user) => (c2)
#| 2 |#
1 (user) => (c2)
#| 3 |#
1 (user) => (c1)
#| 4 |#
1 (user) => (define (make-collector)
(let ((lst '()))
(cons (lambda (new)
(set! lst (cons new lst))
new)
(lambda () lst))))
#| make-collector |#
1 (user) => (define c3 (make-collector))
#| c3 |#
1 (user) => (define c4 (make-collector))
#| c4 |#
1 (user) => ((car c3) 42)
#| 42 |#
1 (user) => ((car c4) 'jerry)
#| jerry |#
1 (user) => ((car c3) 28)
#| 28 |#
1 (user) => ((car c3) 14)
#| 14 |#
1 (user) => ((car c4) 'jack)
#| jack |#
1 (user) => ((cdr c3))
#|
(14 28 42)
|#
1 (user) => c3
#| (#[compound-procedure 29] . #[compound-procedure 30]) |#
1 (user) => (car c3)
#|
(lambda (new)
???)
|#
1 (user) => ((car c3))
;The procedure #[compound-procedure 29] has been called with 0 arguments; it requires exactly 1 argument.
;To continue, call RESTART with an option number:
; (RESTART 1) => Return to read-eval-print level 1.
2 error> (restart 1)
;Abort!
1 (user) => ((cdr c4))
#|
(jack jerry)
|#
1 (user) =>