Worksheet

5.5 Brains

Behaviours · Robot club · about 20 min

What this lesson is about

From a loop to think(me) and me.memory, with a practice arena.

• The loop is outside
• Escape, as a loop
• The same thing as a brain

Questions 6 marks in all

1. [1 mark]How often does the arena call your think(me) function?

   1. ATen times a second
   2. BOnce, at the start of the game
   3. COnly when another robot comes close
   4. DAs fast as the computer can

2. [1 mark]Why does a brain keep its state in me.memory rather than in a normal variable?

   1. ALocal variables are forgotten when the function returns
   2. Bme.memory is faster
   3. CNormal variables cannot hold words
   4. DThe arena reads me.memory to score you

3. [1 mark]What does this program print?

   class Me:
       def __init__(self):
           self.memory = {}
   
   def think(me):
       count = me.memory.get("count", 0)
       me.memory["count"] = count + 1
   
   def forgetful(me):
       count = 0
       count += 1
       return count
   
   me = Me()
   for i in range(3):
       think(me)
       n = forgetful(me)
   print(me.memory["count"])
   print(n)

4. [1 mark]On the very first tick, me.memory is empty. What does me.memory.get("state", "go") give?

   1. A"go", the default
   2. BNone
   3. CAn error, because the key is missing
   4. DAn empty string

5. [1 mark]What does this program print?

   samples = [(20, 0), (25, 45), (60, 90), (80, 135), (70, 180), (30, 225), (20, 270)]
   opens = [h for d, h in samples if d > 40]
   target = opens[len(opens) // 2]
   print(opens, target)

6. [1 mark]The escape program aims at the middle of the open headings, not the single longest reading. Why?

   1. AThe longest reading points at a corner of the opening
   2. BThe longest reading is always wrong
   3. CThe middle is quicker to work out
   4. DThe distance sensor cannot read long distances

The task: escape the box

Three walls around you. Find the gap with the distance sensor, drive out and into the green zone, touching nothing.

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

# as long as the thing ahead is further than 15 cm
while distance() > 15:
    # drive forward at 50 (keeps going until the next command)
    forward(50)
    # pause 0.1 s (the robot keeps doing what it was told)
    wait(0.1)
# all motors off
stop()
print("wall at", distance())

Plan your program here, then type it in and press Run.

Do it on the robot
www.bugbotlab.com/learn/5-5-brains/
The simulator checks it and tells you when it passes. Nothing to install, no account.

Challenges

1. Escape faster: stop looking as soon as you have seen a reading over 40 and the readings are falling again.
2. In the arena, add a third state: "shove", entered when another robot is within 10 cm, that drives at it for five ticks.
3. Write the escape as a brain (think(me) with me.memory) on paper. What changes?