SICP : Let's Read!

2026-09-08T19:18:32+00:00

> SICP Book:
https://mitp-content-server.mit.edu/books/content/sectbyfn/books_pres_0/6515/sicp.zip/full-text/book/book-Z-H-4.html

> SICP Lectures:
https://www.youtube.com/playlist?list=PLE18841CABEA24090
> Racket Scheme
https://racket-lang.org/download/
> SICP Racket
https://docs.racket-lang.org/sicp-manual/Installation.html

Let's embrace the tree structure of Pohon BBS.

Top level comments for chapters of the book,
replies to top level comments for discussions of the chapter.

Comment #2 will be for general help installing Scheme
Comment #3 will be for random Scheme discussion that doesn't
fit into chapter discussion.

Ready, start, go!

Reply to thread

2026-09-08T19:19:01+00:00

General Scheme troubleshooting / installation help / etc goes under this
comment....

Reply to thread

2026-09-08T19:20:17+00:00

Random Scheme / Lisp / programming discussion that doesn't fit into
chapter discussion goes here....

Chapter 1

2026-09-08T19:21:18+00:00

SICP chapter 1
> Building Abstractions with Procedures

https://mitp-content-server.mit.edu/books/content/sectbyfn/books_pres_0/6515/sicp.zip/full-text/book/book-Z-H-9.html#%_chap_1

phatcat power level formula (first scheme test)

2026-09-08T19:24:34+00:00

(define phatcat_powerlevel 1200)
(define unlocked_potential 500)
(define (phatcat_bulky_transformation x y) (* 1.2 (+ x y)))
(phatcat_bulky_transformation phatcat_powerlevel unlocked_potential)

Chapter 2

2026-09-08T19:27:34+00:00

> Building Abstractions with Data
https://mitp-content-server.mit.edu/books/content/sectbyfn/books_pres_0/6515/sicp.zip/full-text/book/book-Z-H-13.html#%_chap_2

Chapter 3

2026-09-08T19:28:36+00:00

> Modularity, Objects, and State

https://mitp-content-server.mit.edu/books/content/sectbyfn/books_pres_0/6515/sicp.zip/full-text/book/book-Z-H-19.html#%_chap_3

Chapter 4

2026-09-08T19:29:38+00:00

> Metalinguistic Abstraction
https://mitp-content-server.mit.edu/books/content/sectbyfn/books_pres_0/6515/sicp.zip/full-text/book/book-Z-H-25.html#%_chap_4

Chapter 5

2026-09-08T19:30:51+00:00

> Computing with Register Machines

https://mitp-content-server.mit.edu/books/content/sectbyfn/books_pres_0/6515/sicp.zip/full-text/book/book-Z-H-30.html#%_chap_5

outputs color based on stats (hopefully)

2026-09-08T19:37:11+00:00

(define (clouds_color strength intelligence Defense)
(define red strength)
(define blue intelligence)
(define green defence)
(list red green blue))) % gives RGB color (idk how to/
if its even possible for lisp to output a color)

some sample lisp code

2026-09-08T19:51:10+00:00

(define pi 3.14159265)
(define (square x) (* x x))

(define (volume-of-cone radius height)
(* pi (square radius) (/ height 3)))

(define my-cone-volume (volume-of-cone 1 2))

my-cone-volume
=> 2.09

Reply to thread

2026-09-08T20:11:17+00:00

Famous article by a guy who used Lisp to become a billionaire :

> Graham, Paul. "The Roots of Lisp." (2001) 15pp
https://wiki.eecs.yorku.ca/course_archive/2014-15/W/6339/_media/jmc.pdf

discusses how 7 primitives became the meta language

exercise 1.3

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%% (define (square x) %%
%% (* x x)) %%
%% (define (sum-squares x y) %%
%% (+ (square x) (square y))) %%
%% %%
%% (define (sum-greater-squares x y z) %%
%% (if (> x y) %%
%% (if (> y z) %%
%% (sum-squares x y) %%
%% (sum-squares x z)) %%
%% (if (> x z) %%
%% (sum-squares y x) %%
%% (sum-squares y z)))) %%
%% %%
%% (sum-greater-squares 1 2 3) %%
%% (sum-greater-squares 4 2 3) %%
%% (sum-greater-squares 5 1 0) %%

Excercise 1.3

2026-09-09T01:43:46+00:00

My attempt at exercise 1.3. it took me a long time as most of my attempts made code that excluded anything that wasn't the maximum number, so i guess finding the "middle" number is what makes this challenging. my first attempts were checking each variable against the others individually (mistake). if x>y then output x otherwise 0, if x>z output x otherwise 0 then multiply both outputs, repeat for each variable (rather silly in retrospect). After this i decided to only compare to the third variable if the first check failed and directly compute the square if the variable wasn't the minimum. Code below:

%%#lang sicp%%
%%(define (sicp_ex_1.3 x y z)%%
%% (+%%
%% (if (< x y) (if (< x z) 0 (* x x)) (* x x))%%
%% (if (< y x) (if (< y z) 0 (* y y)) (* y y))%%
%% (if (< z y) (if (< z x) 0 (* z z)) (* z z))))%%
%% %%
%%(sicp_ex_1.3 1 2 3)%%
%%result was 13 so it worked%%

corrected exercise 1.3

2026-09-09T15:22:45+00:00

%%%
Updated to catch PhatCat's fix -- if x, y, and z are the same
value, the code does not work

(define (square x)
(* x x))
(define (sum-squares x y)
(+ (square x) (square y)))

(define (sum-greater-squares x y z)
(if (> x y)
(if (> y z)
(sum-squares x y)
(sum-squares x z))
(if (> x z)
(sum-squares y x)
(if (= x y z)
(sum-squares x x)
(sum-squares y z)))))
%%%

fix ex 1.3

2026-09-09T15:27:28+00:00

summed all 3 squares if x y z were the same. added a check to just force one variable to zero if all the numbers were equal so theres probably a more elegant solution :P. Code:

%%#lang sicp%%

%%(define (square x) (* x x))%%

%%(define (sicp_ex_1.3 x y z)%%
%% (+%%
%% (if (= x y) 0 (if (= x z) 0%%
%% (if (< x y) (if (< x z) 0 (square x)) (square%% %%x))))%%
%% (if (< y x) (if (< y z) 0 (square y)) (square y))%%
%% (if (< z y) (if (< z x) 0 (square z)) (square z))))%%

%%(sicp_ex_1.3 1 2 3)%%
%%(sicp_ex_1.3 2 2 2)%%
%%(sicp_ex_1.3 2 1 0)%%

epic phail

2026-09-09T15:35:08+00:00

Fixed the fix

%%#lang sicp%%

%%(define (square x) (* x x))%%

%%(define (sicp_ex_1.3 x y z)%%
%% (+%%
%% (if (= x y z) 0%%
%% (if (< x y) (if (< x z) 0 (square x)) (square x))))%%
%% (if (< y x) (if (< y z) 0 (square y)) (square y))%%
%% (if (< z y) (if (< z x) 0 (square z)) (square z)))%%

%%(sicp_ex_1.3 1 2 3)%%
%%(sicp_ex_1.3 2 2 2)%%
%%(sicp_ex_1.3 2 1 0)%%

exercise 1.3

2026-09-09T20:55:03+00:00

%%%
[(define (square a)
(* a a))

(define (smallest x y z)
(if (< x y)
(if (< x z) x z)
(if (< y z) y z)))

(define (procedure x y z)
(- (+ (square x)(square y)(square z))(square (smallest x y z))))

(procedure 7 10 10)]
%%%