alice-teacher Major flaw in Alice 2

[robert durtschi]

Rare but annoying when it happens.

We are doing an Alice world where we are using events to control a seaplane.  There is no need for anything but events, so for a change I immediately deleted 'my first method' from "when the world starts" and changed the event to "while the world is running, during: seaplane move forward 1 meter.

Later in the exercise we added a speed control:

    create a Seaplane properties variable called "speed"

    replace the 1 meter in "seaplane move forward 1 meter" with "speed meters"

    choose two "when a key is pressed" 'A' and 'D' to "increment speed by 1" (Accelerate) and "decrement speed by 1" (Decelerate).

    We needed a guard check to keep speed from going negative: "if speed > 0" decrement speed by 1


That's when I realized that the 'universal' commands at the bottom of the edit window, including the if/else had disappeared along with the edit window for the "my first method" I created a method long enough to get the if/else back then deleted it again.


Bob Durtschi

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