1. Ionut Trestian Northwestern University
EECS 110: Recitation #1:
Ionut Trestian
Northwestern University

2. If statements (1) hw0pr1.py Homework 0, problem 1
name = raw_input('Hi... what is your name? ')
if name == 'Ionut': # is it Ionut?
print 'x1'
else: # in all other cases...
print 'x2'
print 'x3'
hw0pr1.py
Homework 0, problem 1

3. If statements (2) name = raw_input('Hi... what is your name? ')
if name == 'Ionut‘:
print 'x1'
else:
print 'x2'
print 'x3'

4. If statements (3) hw0pr1.py Homework 0, problem 1
name = raw_input('Hi... what is your name? ')
if name == 'Ionut': # is it Ionut?
print 'x1'
elif name == 'Aleksandar':
print 'x2'
else: # in all other cases...
print 'x3'
print 'x4'
hw0pr1.py
Homework 0, problem 1

5. If statements (4) name = raw_input('Hi... what is your name? ')
if name == 'Ionut':
print 'x1'
elif name == 'Aleksandar':
print 'x2'
else:
print 'x3'
print 'x4'

6. If statements (5) hw0pr1.py Homework 0, problem 1
name = raw_input('Hi... what is your name? ')
if name == 'Ionut': # is it Ionut?
print 'x1'
elif name == 'Aleksandar':
print 'x2'
elif name == 'Lisa':
print 'x3'
else: # in all other cases...
print 'x4'
print 'x5'
hw0pr1.py
Homework 0, problem 1

7. If statements (6) name = raw_input('Hi... what is your name? ')
if name == 'Ionut‘:
print 'x1'
elif name == 'Aleksandar’:
print 'x2'
elif name == 'Lisa':
print 'x3'
else:
print 'x4'
print 'x5'

8. Goal: whole-environment coverage with only local sensing…
Homework problems 3 and 4
walls
Picobot
Picobot
area not covered (yet!)
area already covered
Goal: whole-environment coverage with only local sensing…
inspiration?

9. Goal: whole-environment coverage with only local sensing…
Picobot
walls
Picobot
area not covered (yet!)
area already covered
Goal: whole-environment coverage with only local sensing…
iRobot's Roomba vacuum
inspiration!

10. NxWx Surroundings N E W S
Picobot can only sense things directly to the N, E, W, and S N W E S
For example, here its surroundings are
NxWx
Surroundings are always in NEWS order.
N E W S

11. How many distinct surroundings are there?24
== 16 possible …
xxxx
Nxxx
xExx
xxWx
xxxS
NExx
NxWx
NxxS
xEWx
xExS
xxWS
NEWx
NExS
NxWS
xEWS
NEWS
(won’t happen)

12. State
I am in state 0.
My surroundings
are xxWS.
Picobot's memory is a single number, called its state.
State is the internal context of computation.
Picobot always starts in state 0.
State and surroundings represent everything the robot knows about the world

13. Rules Aha! I should move N. I should enter state 0.
I am in state 0.
My surroundings
are xxWS.
Aha!
I should move N.
I should enter state 0.
Picobot moves according to a set of rules:
state
surroundings
direction
new state
xxWS N
If I'm in state 0 seeing xxWS,
Then I move North, and change to state 0.

14. here, EWS may be wall or empty space
Wildcards
I am in state 0.
My surroundings
are xxWS.
Aha! This matches x***
Asterisks * are wild cards They match walls or empty space:
state
surroundings
direction
new state
x*** N
here, EWS may be wall or empty space

15. x*** -> N*** -> ***x -> ***S ->
What will this set of rules do to Picobot?
state
surroundings
direction
new state
x***
-> N
N***
-> X 1 1
***x
-> S 1 1
***S
-> X
Picobot checks its rules from the top each time.
When it finds a matching rule, that rule runs.
Only one rule is allowed per state and surroundings.

16. To do hw0, Problem #3 hw0, Problem #4 (Extra)
Write rules that will always cover these two rooms.
(separate sets of rules are encouraged…)
hw0, Problem #3
hw0, Problem #4 (Extra)
but your rules should work regardless of Picobot's starting location

17. Alter these "up & down" rules so that Picobot will traverse the empty room…

18. Ideas for the maze?
Hold on to one wall !!
the maze