Intro to Robots

1
Lab 3
2
Basic Robot Brain

• Programs consist of import lines, function
  definitions and and a starting point.

Line 1 from myro import Line 2
initialize("comX") Line 3 imports Line 4 Line 5
def main() Line 6 Line 7
Line 8 ... Line 9 main()
Always start from a function called main()
3
Exercise

• Combine the following functions into a program
  that yoyos and wiggles for a bit. Try to make
  your dance short and sweet.

def yoyo(speed, waitTime) forward(speed,
waitTime) backward(speed, waitTime)
stop()
def wiggle(speed, waitTime) motors(-speed,
speed) wait(waitTime) motors(speed,
-speed) wait(waitTime) stop()
4
Exercise

• Take the previous program and rename the main()
  function dance().
• Now create a main() function that calls dance().
• The problem is if you want to dance all night.
• Call the program dance.py.
• It works but not very interesting

def main() dance() dance() dance()
dance() . . .
5
Repetition in Python (and other languages)

• Programming languages have syntax for repeating
  the same thing over and over and over and over .
  . .
• for-loop when you know exactly how many times to
  repeat something
• while-loop when you dont know, in advance,
  exactly how many times you need to repeat
  something

def main() for i in range(1) dance()
keeps calling dance()until 10 seconds havepassed
def main() while timeRemaining(10)
dance()
6
Exercise

• Modify the dance.py program to use a for-loop.

7
While-Loops

• c(i) is a boolean condition that is True of False
  depending on the value of i.
• f() gives a new value to i, once for each
  iteration through the loop.
• This loop will go on forever if f() never returns
  a value for which c(i) False.

i 0 while c(i) do something i f()
answer Nowhile answer No dance()
answer ask(Again?)
what happens if you never enter Nobut rather
no, n, NO, etc.
8
Infinite Loops

• The example on the last slide shows that a loop
  can, by accident, go on forever. You can also
  intentionally write an infinite loop.
• How do you stop this loop?

while True do something
Ctrl-C
9
Exercise

• Modify the dance.py program to replace the
  for-loop with a while-loop.
• Try various while-loops including an infinite
  loop.