Decomposition

Hurdles 👩🏼‍🎨

• What pattern or strategy best fits this problem?

• What verbs would make this problem easy to solve?

NOTES

The event stream pattern works well: the event is running into a jumpable wall (left clear). The event loop runs until Bit cannot jump anymore.

• You can also use "up" and "drop" as events with an if/else as opposed to a single "jump hurdle" event
  • But this is a bit tricky: the order of conditions is critical

• Note that "up" and "over" are similar, vs "down"

Elevators 👨🏼‍🎨

elevators.py

Bit needs to climb to the top of the building, using the green elevators.

NOTES

This activity prepares the students for waterfall.py in the lab.

• Draw it out!
• Pose the problem as an event stream problem
• What is the outer loop?
• What is the condition that triggers the event?
  • What is the event?
• How do we rise?
  • What is the while condition?
  • What is the glue code before and after the "rise" loop?
• Use comments to indicate subgoals

More Elevators

Now write a single function that can allow Bit to travel in either direction.

NOTES

Add in 'more-elevators' as a test case. Observe the problem: Bit turns into the floor when heading from left to right.

How do we know which way to turn to rise?

Similar "rise" blocks: each has a while loop, but the turns are different.

Key Ideas

• abstraction: create the pieces that will solve the problem
• boundary conditions: knowing how the pieces fit together