IS 313 Today

1
IS 313 Today
Strings, lists, and loops beyond 1d !
What's ahead?
10/7 Lec 5 today, now!
10/8 homework 3 due
10/14 Lec 6 "dictionaries"
10/15 homework 4 due
HMC Fall Break
http//www.asciimation.co.nz/
10/28 Lec 7 classes objects
11/29 homework 5 due
I see I'm not the only one loopy around here
HMC standings!?
2
An image alternative
3
ASCII Art
Print 4 rows
for row in range(3) print 4
print automaticallyadds a newline
Creates line to print

Output
4
A closer look
for row in range(3) print ''4

Output
5
No string !
for row in range(3) print ''4

For this problem, string multiplication is not
allowed.
Output
6
Without string multiplication
Print 3 rows
for row in range(3) for col in range(4)
print ''
nested loops!
print 4 chars on each line
(columns)
Output ?
7
Without string multiplication
Print 3 rows
for row in range(3) for col in range(4)
print '',
nested loops!
print 4 chars on each line
(columns)
Comma suppresses newline
Output ?
8
Without string multiplication
Print 3 rows
for row in range(3) for col in range(4)
print '', print
nested loops!
print 4 chars on each line
(columns)

Comma suppresses newline
plain print produces newline
tracking cols and rows!
9
Tracking rows and columns
for row in range(3) for col in range(4)
print '', print

Output
10
Variations!
def rectangle( width, height ) """ prints a
rectangle of """
for row in range( ) for col in
range( ) print '', print
11
"Quiz"
Fill in each block of code so that it will print
the lines above it.
0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6
0 1 2 3 4 5 6 1 2 3 4 5 6 7 2 3 4 5 6 7 8
for row in range( 3 ) for col in range( 7
) print ____________, print
for row in range( 3 ) for col in range( 7
) print ____________, print
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0
0 0 0 0 0 0 0 1 1 1 1 1 1 1 2 2 2 2 2 2 2
for row in range( 3 ) for col in range( 7
) print _____________, print
for row in range( 3 ) for col in range( 7
) print ______________, print
12
Beyond boxes
What code would print this ASCII triangle ?
with height rows and width columns
1
cols
2
3
4
5
6
7
rows
for row in range(1,7)

1
2
for col in range( )
3
4
5
6
13
A video alternative ?!?
http//www.asciimation.co.nz/
14
A simpler web interface
HTML
HyperText Markup Language
ltbgtand the beautifullt/bgt ltbrgt
ltigtTower of Pisalt/igt
15
A simpler web interface
HTML
HyperText Markup Language
ltbgtand the beautifullt/bgt ltbrgt
ltigtTower of Pisalt/igt
CGI
Common Gateway Interface HTML forms
ltform action"test.cgi"gt ltinput type"text"
name"message" /gt lt/formgt
16
A simpler web interface
HTML
HyperText Markup Language
ltbgtand the beautifullt/bgt ltbrgt
ltigtTower of Pisalt/igt
CGI
Common Gateway Interface HTML forms
ltform action"test.cgi"gt ltinput type"text"
name"message" /gt lt/formgt
CSS
AJAX
Javascript
Others!
17
Web resources on the Web
www.w3schools.com
every technology - and acronym - you'd ever want
to know
started by
Tim Berners-Lee
18
This week
Get the pure-Python webserver and run it.
Make sure the example "application" works
Change the example "application" so that you
web-implement one of the ASCII art problems
Checklist

• be sure that you take in the inputs you need

• watch out for conversions between ints and
  strings!

• make small changes and test as you go

This is not webdesign!
19
Strings vs. language
humans
ideas / meaning
language / words / phrases
strings
numbers / bits
computers
20
Turing Test
How could a computer demonstrate intelligence?
100,000 Loebner prize for passing the Turing
test, held each year in the London Museum of
Science
Alan Turing
Hugh Loebner
Confederates
www.abenteuermedien.de/jabberwock/index.php
21
Parsing for real
Time flies like an arrow, but fruit flies like a
banana.
I like bananas, too!
- Marx
"lttimegt" "time" ltgt N NOM SG
_at_SUBJ "ltfliesgt" "fly" ltSVOgt ltSVgt V PRES
_at_FMAINV "fly" N NOM PL _at_NPHR "ltlikegt" "like"
PREP _at_ltNOM "ltangt" "an" ltIndefgt DET CENTRAL
ART "lt2-NLgt" "ltarrowgt" "arrow" N NOM SG
_at_NPHR "lt\,gt" "ltbutgt" "but" CC
_at_CC "ltfruit_fliesgt" "fruit_fly" N NOM PL
_at_NPHR "ltlikegt" "like" PREP _at_ltNOM "ltagt" "a"
ltIndefgt DET CENTRAL ART "ltbananagt" "banana" N
NOM SG _at_ltP "lt.gt"
(S (S (NP Time flies) (VP like
(NP an arrow))) , but (S (NP fruit)
(VP flies (PP like (NP a
banana)))) .)
http//www.link.cs.cmu.edu/link/submit-sentence-4.
html
parseTree 1
http//www.lingsoft.fi/cgi-bin/engcg
parseTree 2
22
Some conversations
Jabb... Greetings! Jabberwock is at the
keyboard. You... How are you doing? Jabb...
Everything is running smoothly. And how are you
doing? You... Pretty well. It's quiet around
here this morning. Jabb... Does that mean you
agree? You... Agree with what? Jabb...
Sure.
2005 and 2006 winner Rollo Carpenter's
Jabberwacky
23
Loebner results
2003
no human averaged less than 80
four humans and four machines participated
2005
24
Some conversations
You Hi. youre the program that won the Loebner
competition, right? SID Albert One was the
last winner of the Loebner Contest. I am
something else entirely. You Impressive. Do
you have any areas of particular expertise?
25
Some conversations
You Hi. youre the program that won the Loebner
competition, right? SID Albert One was the
last winner of the Loebner Contest. I am
something else entirely. You Impressive. Do
you have any areas of particular expertise? SID
I appreciate that. You Not so impressive. If
I ask a question after a statement, do you
ignore the question?
26
Some conversations
You Hi. youre the program that won the Loebner
competition, right? SID Albert One was the
last winner of the Loebner Contest. I am
something else entirely. You Impressive. Do
you have any areas of particular expertise? SID
I appreciate that. You Not so impressive. If
I ask a question after a statement, do you
ignore the question? SID I am free to do as
I please. You Wow! Are you talking free will
vs. determinism?
27
Some conversations
You Hi. youre the program that won the Loebner
competition, right? SID Albert One was the
last winner of the Loebner Contest. I am
something else entirely. You Impressive. Do
you have any areas of particular expertise? SID
I appreciate that. You Not so impressive. If
I ask a question after a statement, do you
ignore the question? SID I am free to do as
I please. You Wow! Are you talking free will
vs. determinism? SID I dont think wow am i
talking free will vs. determinism, but I
cant be 100 sure of that.
28
Computing with language
open questions in AI
ideas / meaning
(1)
language / words / phrases
computing with language - recognizing English!
(2)
strings
how strings are represented and stored
(3)
numbers / bits
29
Caesar Cipher
'Bzdrzq bhogdq? H oqdedq Bzdrzq rzkzc.' 'Caesar
cipher? I prefer Caesar salad.'
30
Caesar Cipher encipher
'gv vw dtwvg' 'hw wx euxwh'
encipher( 'gv vw dtwvg', 0 )
encipher( 'gv vw dtwvg', 1 )
31
Caesar Cipher encipher
'gv vw dtwvg' 'hw wx euxwh' 'ix xy fvyxi' 'jy yz
gwzyj' 'kz za hxazk'
encipher( 'gv vw dtwvg', 0 )
encipher( 'gv vw dtwvg', 1 )
encipher( 'gv vw dtwvg', 2 )
encipher( 'gv vw dtwvg', 3 )
encipher( 'gv vw dtwvg', 4 )
. . .
'fu uv csvuf'
encipher( 'gv vw dtwvg', 25 )
should return the string s with each alphabetic
character shifted/wrapped by n places in the
alphabet
encipher( s , n )
32
ASCII
American Standard Code for Information Interchange
low-tech art form!
33
ASCII
__
_ ,___,-'",--. __,-- _
_,-'_)_ (""'-._\ . _,' __ ,' ,-'
__) ,- /. ,'_,--' -' _)/
\ ,',' ,' ,-'_,
,' ,-' ,(,-(
,' ,-' , _ /
,-._/---' / /
(____)(----. ) ,' / (
.__, /\ /, -.___
/__\/ ,' --. -,\
/ \ .__/ \
(__ \ _ \ ,-,
/ _,\ \ ,' -. ,'_,-' \
(_\,-' ,'\")--,'-' __\
\ / // ,' ,--' -. -.
-/ \' _,' . -._ /
--'/ \ -doh!- ,'
\ /
\ ,-'
/ /
-'
American Standard Code for Information Interchange
low-tech art form!
ASCII-betical order
min
42.42
Homer
Marge
)
bart
lisa
max
34
ASCII
American Standard Code for Information Interchange
ASCII is a table that tells the computer how to
represent characters as s
chr
convert to char.
You know, these functions kind of look familiar!
convert to number
ord
35
ASCII
American Standard Code for Information Interchange
ASCII is a table that tells the computer how to
represent characters as bits!
value
''
00101010
bits
type str
name
Identical bits are stored in each variable!
8 bits 1 byte
The types determine how to interpret the bits
the names don't matter at all
value
42
00101010
The SAME bits represent integers, if the variable
has type int instead of str
bits
type int
name
36
chr and ord
abcdefghijklmnopqrstuvwxyz
ASCII VALUES
97
122
99
101
103
105
107
109
111
113
115
117
119
ABCDEFGHIJKLMNOPQRSTUVWXYZ
65
90
67
69
71
73
75
77
79
81
83
87
85
Input a string of one character, c
ord( c )
Output an integer, the ASCII value of c
CONVERTERS
Input an integer in range(255)
chr( n )
Output a one-char. string of that ASCII value
for i in range(128) print 'i and chr(i)
are', i, chr(i)
try this
37
chr and ord
abcdefghijklmnopqrstuvwxyz
ASCII VALUES
97
122
99
101
103
105
107
109
111
113
115
117
119
ABCDEFGHIJKLMNOPQRSTUVWXYZ
65
90
67
69
71
73
75
77
79
81
83
87
85
ord('a') is 97
chr(66) is 'B'
What is chr( ord('i')13 )
What is chr( ord('W')13 ) ?
How can we wrap this around?
38
Rot 13
def adv13( c ) """ rotates c by 13 chars,
"wrapping" as needed NON-LETTERS DO NOT
CHANGE! """ if 'a' lt c lt 'z'
new_ord ord(c) 13 if new_ord lt
ord('z') return chr(new_ord)
no wrapping else return
elif else
How would you rotate an entire string?
39
Caesar Cipher decipher
gtgtgt decipher('Bzdrzq bhogdq? H oqdedq Bzdrzq
rzkzc.') 'Caesar cipher? I prefer Caesar salad.'
gtgtgt decipher('Hu lkbjhapvu pz doha ylthpuz hmaly
dl mvynla '\ 'lclyfaopun dl ohcl
slhyulk.') 'An education is what remains after we
forget everything we have learned.'
gtgtgt decipher('gv vw dtwvg')
But how ?
40
Caesar Cipher decipher
gv vw dtwvg hw wx euxwh ix xy fvyxi jy yz
gwzyj kz za hxazk la ab iybal mb bc jzcbm nc cd
kadcn od de lbedo pe ef mcfep qf fg ndgfq rg gh
oehgr sh hi pfihs ti ij qgjit uj jk rhkju vk kl
silkv wl lm tjmlw xm mn uknmx yn no vlony zo op
wmpoz ap pq xnqpa bq qr yorqb cr rs zpsrc ds st
aqtsd et tu brute fu uv csvuf
Caesar
Brutus
gtgtgt decipher('gv vw dtwvg')
Strategy using max
(1) consider all possible answers
(2) give them each a score
(3) loop through them all and find the one with
the max score!
Score for "Englishness"?
up to you
all 26 possibilities
41
Caesar Cipher decipher
0, 'cr rs zpsrc' 0, 'gv vw dtwvg' 0, 'jy yz
gwzyj' 0, 'mb bc jzcbm' 0, 'qf fg ndgfq' 0,
'wl lm tjmlw' 1, 'bq qr yorqb' 1, 'ds st
aqtsd' 1, 'nc cd kadcn' 1, 'vk kl silkv' 1,
'xm mn uknmx' 2, 'ap pq xnqpa' 2, 'hw wx
euxwh' 2, 'ix xy fvyxi' 2, 'kz za hxazk' 2,
'rg gh oehgr' 2, 'sh hi pfihs' 2, 'uj jk
rhkju' 2, 'yn no vlony' 3, 'fu uv csvuf' 3,
'pe ef mcfep' 3, 'ti ij qgjit' 3, 'zo op
wmpoz' 4, 'et tu brute' 4, 'la ab iybal' 4,
'od de lbedo'
Caesar
Brutus
gtgtgt decipher('gv vw dtwvg') 'od de lbedo'
Strategy using max
(1) consider all possible answers
(2) give them each a score
(3) use our techniques with max
number-of-vowels score
won't always be correct!
all 26 possibilities
42
Caesar Cipher decipher
0.4680, 'jy yz gwzyj' 0.4960, 'mb bc
jzcbm' 0.5420, 'uj jk rhkju' 0.5567, 'ix xy
fvyxi' 0.5597, 'qf fg ndgfq' 0.5718, 'fu uv
csvuf' 0.5753, 'bq qr yorqb' 0.5833, 'kz za
hxazk' 0.5859, 'xm mn uknmx' 0.5880, 'gv vw
dtwvg' 0.5902, 'vk kl silkv' 0.6110, 'ap pq
xnqpa' 0.6304, 'zo op wmpoz' 0.6318, 'wl lm
tjmlw' 0.6717, 'cr rs zpsrc' 0.6735, 'hw wx
euxwh' 0.6963, 'nc cd kadcn' 0.7153, 'ti ij
qgjit' 0.7398, 'la ab iybal' 0.7442, 'yn no
vlony' 0.7867, 'pe ef mcfep' 0.7880, 'sh hi
pfihs' 0.7918, 'rg gh oehgr' 0.8213, 'ds st
aqtsd' 0.8609, 'od de lbedo' 0.9082, 'et tu
brute'
Caesar
Brutus
gtgtgt decipher('gv vw dtwvg') 'et tu brute'
Strategy using max
(1) consider all possible answers
(2) give them each a score
(3) use our techniques with max
letter- probability score
not always correct, but better!
all 26 possibilities
43
The caesar cipher problem offers lots of
freedom Think a bit about how you'll approach it!
Questions / Lab time
44
Caesar Cipher decipher
gtgtgt decipher('Bzdrzq bhogdq? H oqdedq Bzdrzq
rzkzc.') 'Caesar cipher? I prefer Caesar salad.'
gtgtgt decipher('Hu lkbjhapvu pz doha ylthpuz hmaly
dl mvynla '\ 'lclyfaopun dl ohcl
slhyulk.') 'An education is what remains after we
forget everything we have learned.'
gtgtgt decipher('gv vw dtwvg') ?
gtgtgt decipher('Uifz xpsl ju pvu xjui b qfodjm!') ?
But how to do this ?
45
Caesar Cipher decipher
gv vw dtwvg hw wx euxwh ix xy fvyxi jy yz
gwzyj kz za hxazk la ab iybal mb bc jzcbm nc cd
kadcn od de lbedo pe ef mcfep qf fg ndgfq rg gh
oehgr sh hi pfihs ti ij qgjit uj jk rhkju vk kl
silkv wl lm tjmlw xm mn uknmx yn no vlony zo op
wmpoz ap pq xnqpa bq qr yorqb cr rs zpsrc ds st
aqtsd et tu brute fu uv csvuf
Caesar
Brutus
gtgtgt decipher('gv vw dtwvg') ???
Strategy using max
(1) consider all possible answers
(2) give them each a score
(3) use our techniques to get max
Score for "Englishness"?
up to you
all 26 possibilities
46
Caesar Cipher decipher
0, 'cr rs zpsrc' 0, 'gv vw dtwvg' 0, 'jy yz
gwzyj' 0, 'mb bc jzcbm' 0, 'qf fg ndgfq' 0,
'wl lm tjmlw' 1, 'bq qr yorqb' 1, 'ds st
aqtsd' 1, 'nc cd kadcn' 1, 'vk kl silkv' 1,
'xm mn uknmx' 2, 'ap pq xnqpa' 2, 'hw wx
euxwh' 2, 'ix xy fvyxi' 2, 'kz za hxazk' 2,
'rg gh oehgr' 2, 'sh hi pfihs' 2, 'uj jk
rhkju' 2, 'yn no vlony' 3, 'fu uv csvuf' 3,
'pe ef mcfep' 3, 'ti ij qgjit' 3, 'zo op
wmpoz' 4, 'et tu brute' 4, 'la ab iybal' 4,
'od de lbedo'
Caesar
Brutus
gtgtgt decipher('gv vw dtwvg') 'od de lbedo'
Strategy using max
(1) consider all possible answers
(2) give them each a score
(3) use our techniques with max
Score for "Englishness"?
up to you
won't always be correct!
all 26 possibilities
47
Caesar Cipher decipher
0.4680, 'jy yz gwzyj' 0.4960, 'mb bc
jzcbm' 0.5420, 'uj jk rhkju' 0.5567, 'ix xy
fvyxi' 0.5597, 'qf fg ndgfq' 0.5718, 'fu uv
csvuf' 0.5753, 'bq qr yorqb' 0.5833, 'kz za
hxazk' 0.5859, 'xm mn uknmx' 0.5880, 'gv vw
dtwvg' 0.5902, 'vk kl silkv' 0.6110, 'ap pq
xnqpa' 0.6304, 'zo op wmpoz' 0.6318, 'wl lm
tjmlw' 0.6717, 'cr rs zpsrc' 0.6735, 'hw wx
euxwh' 0.6963, 'nc cd kadcn' 0.7153, 'ti ij
qgjit' 0.7398, 'la ab iybal' 0.7442, 'yn no
vlony' 0.7867, 'pe ef mcfep' 0.7880, 'sh hi
pfihs' 0.7918, 'rg gh oehgr' 0.8213, 'ds st
aqtsd' 0.8609, 'od de lbedo' 0.9082, 'et tu
brute'
Caesar
Brutus
gtgtgt decipher('gv vw dtwvg') 'et tu brute'
Strategy using max
(1) consider all possible answers
(2) give them each a score
(3) use our techniques to get max
Score for "Englishness"?
up to you
depends on how you score
all 26 possibilities
48
Caesar Cipher encipher
'gv vw dtwvg' 'hw wx euxwh' 'ix xy fvyxi' 'jy yz
gwzyj' 'kz za hxazk' 'la ab iybal'
encipher( 'gv vw dtwvg' , 0 )
encipher( 'gv vw dtwvg' , 1 )
encipher( 'gv vw dtwvg' , 2 )
encipher( 'gv vw dtwvg' , 3 )
encipher( 'gv vw dtwvg' , 4 )

encipher( 'gv vw dtwvg' , 5 )
'fu uv csvuf'
encipher( 'gv vw dtwvg' , 25 )
should return the string s with each alphabetic
character shifted/wrapped by n places in the
alphabet
encipher( s , n )
Historically bad decision 43
Brutus won't mind if I use his salary to bring
Justin Timberlake to the Colosseum next month...
49
CHR and ORD
Orchard Field
50
CHR and ORD
Chateauroux
51
Mutable vs. Immutable data
Changeable types
Unchangeable types
tuple
dictionary
float
string
list
bool
int
x 42
42
x
What's a dictionary?
I guess I'll have to look it up!
52
Reference vs. Value
Changeable types
Unchangeable types
tuple
dictionary
float
string
list
bool
int
L 5,42,'hi'
x 42
Reference, Pointer, id
42
42
'hi'
5
L
x
L0
L1
L2
53
Pass By Value
def main() """ calls conform """ print "
Welcome to Conformity, Inc. " fav 7
conform(fav) print " My favorite number is",
fav def conform(fav) """ sets input to
42 """ fav 42 return fav
7
fav
fav
54
Pass By Value
def main() """ calls conform """ print "
Welcome to Conformity, Inc. " fav 7
conform(fav) print " My favorite number is",
fav def conform(fav) """ sets input to
42 """ fav 42 return fav
7
fav
PASS BY VALUE
7
42
fav
Pass by value means that data is copied when
sent to a method
55
Passing lists by value
def main() """ calls conform2 """ print "
Welcome to Conformity, Inc. " fav 7, 11
conform2(fav) print " My favorite
numbers are", fav def conform2(fav)
""" sets all of fav to 42 """ fav0 42
fav1 42
42
5
fav
L0
L1
fav
What gets passed by value here?
56
Passing lists by value
def main() """ calls conform2 """ print "
Welcome to Conformity, Inc. " fav 7, 11
conform2(fav) print " My favorite
numbers are", fav def conform2(fav)
""" sets all of fav to 42 """ fav0 42
fav1 42
42
5
fav
L0
L1
The reference is copied!
fav
can change data elsewhere!
57
The conclusion
You can change the contents of lists in functions
that take those lists as input.
(actually, lists or any mutable objects)
Those changes will be visible everywhere.
(immutable objects are safe, however)
58
Views of the world
Engineers think their equations approximate
reality.
59
Views of the world
Engineers think their equations approximate
reality. Physicists think reality approximates
their equations.
60
Views of the world
Engineers think their equations approximate
reality. Physicists think reality approximates
their equations. Mathematicians don't care.
61
Views of the world
Engineers think their equations approximate
reality. Physicists think reality approximates
their equations. Mathematicians don't care. 
Creating structure from a few simple actions ...
Creating structure from a few simple facts...
for
arrays
variables
Axioms
while
Definitions
arithmetic operations
if/else
Proof
Algorithm
62
Lists flexibility
Lists can hold ANY type of data
A 42., 75., 70.
42.0
75.0
70.0
float
float
float
list
A
they dont have to be horizontal lists!
63
Lists flexibility
Lists can hold ANY type of data
A 42., 75., 70.
42.0
75.0
70.0
float
float
float
list
A
42.0
list
double
they dont have to be horizontal lists!
A
75.0
double
70.0
double
64
Lsits flexibility
Lists can hold ANY type of data
42.0
75.0
70.0
double
double
list
double
A
42
7
-11
int
int
list
int
A
go
red
sox!
String
String
list
String
A
65
2d lists or arrays
Lists can hold ANY type of data -- including
lists !
A 1,2,3,4, 5,6, 7,8,9,10,11
list
A
66
2d arrays
Lists can hold ANY type of data -- including
lists !
A 1,2,3,4, 5,6, 7,8,9,10,11
list
list
A0
A
list
A1
list
A2
67
Jagged arrays
Lists can hold ANY type of data -- including
lists !
A 1,2,3,4, 5,6, 7,8,9,10,11
list
list
A0
A
list
A1
list
A2
Rows within 2d arrays need not be the same length
68
We will not use jagged arrays
at least in hw 10
Lists can hold ANY type of data -- including
lists !
A 1,2,3,4, 5,6, 7,8,9,10,11
list
list
A0
A
list
A1
list
A2
Rows within 2d arrays need not be the same length
69
Rectangular arrays
A12 42
list
list
A0
A
A00
list
A1
list
A2
A23
What does each component of A12 mean ?
How many rows does A have, in general ?
How many columns does A have, in general ?
70
Creating a 2d array
def create2dArray( width, height ) """ does
just that """ A start with
nothing for row in range( height )
for col in range( width ) return A
71
Displaying a 2d array
import csplot
Be sure to download the newest version of this
file
B create2dArray( 10, 10 ) csplot.show( B
) B18 1 set this item to
1 csplot.show( B )
nearby coordinates
72
Problem 2 -- Life
John Conway
Grid World
red cells are alive
Evolutionary rules

• Everything depends on a cells eight neighbors

• Exactly 3 neighbors give birth to a new, live
  cell!

• Exactly 2 or 3 neighbors keep an existing cell
  alive

• Any other number of neighbors kill the central
  cell (or keep it dead)

white cells are empty
73
Problem 2 -- Life
Grid World
red cells are alive
Evolutionary rules

• Everything depends on a cells eight neighbors

• Exactly 3 neighbors give birth to a new, live
  cell!

• Exactly 2 or 3 neighbors keep an existing cell
  alive

• Any other number of neighbors kill the central
  cell (or keep it dead)

white cells are empty
74
Problem 2 -- Life
Grid World
red cells are alive
Evolutionary rules

• Everything depends on a cells eight neighbors

• Exactly 3 neighbors give birth to a new, live
  cell!

• Exactly 2 or 3 neighbors keep an existing cell
  alive

• Any other number of neighbors kill the central
  cell (or keep it dead)

white cells are empty
75
Problem 2 -- Life
Grid World
red cells are alive
Evolutionary rules

• Everything depends on a cells eight neighbors

• Exactly 3 neighbors give birth to a new, live
  cell!

• Exactly 2 or 3 neighbors keep an existing cell
  alive

• Any other number of neighbors kill the central
  cell (or keep it dead)

Keep going!
white cells are empty
life out there...
76
Problem 2 -- Creating Life
B update( B )
new generation or "board"
old generation or "board"
0
1
2
3
4
5
0
1
2
3
4
5
0
0
1
1
2
2
3
3
4
4
5
5
77
Problem 2 -- Creating Life
B update( B )
new generation or "board"
old generation or "board"
0
1
2
3
4
5
0
1
2
3
4
5
0
0
1
1
2
2
3
3
4
4
5
5
78
Problem 2 -- Details
B update( B )
new generation or "board"
old generation or "board"
For each generation

• 0 represents an empty cell
• 1 represents a living cell
• outermost edge should always be left empty (even
  if there are 3 neighbors)
• compute all cells based on their previous
  neighbors before updating any of them

http//www.math.com/students/wonders/life/life.htm
l
life out there...
79
Problem 2 -- to ? and beyond!
"rocks"

• Are there stable life configurations?

"plants"

• Are there oscillating life configurations?

period 3
period 2
"animals"

• Are there self-propagating life configurations?

80
Problem 2 -- to ? and beyond!

• Are there life configurations that expand
  forever?

• What is the largest amount of the life universe
  that can be filled with cells?

• Are all feasible configurations reachable?

• How sophisticated can the structures in the life
  universe be?

Google for GOLLY, Game of Life
81
Lab Homework
82
Without extra spaces
import sys for i in range(4) for j in
range(8) sys.stdout.write('') print
method (function) that prints only its input
software object representing the screen's
standard output

Output