ResetStateEachLoopIteration

DRAFT

Correction

Here is what's right.

If a loop body changes the state of the system (e.g., the position or direction of the sprite, or the value of a variable), then the next iteration of the loop body will see that updated state.

A loop iteration starts with the state left behind from everything that happened before, including all prior loop iteration.

Example with Variable

The following script will make the sprite say: 1, 2, 3, 4.

Students may incorrectly assume that it causes the sprite to say: 1, 1, 1, 1.

Example with Sprite State

The following script rotates the sprite by a total of 180 degrees. The state of the sprite (its direction) changes in the first iteration by 90 degrees, and in the second iteration by another 90 degrees, for a total of 180 degrees.

Students with the misconception might believe that the sprite only rotates a total of 90 degrees.

Symptoms

How do you know your students might have this misconception?

Empirical Evidence

Grover and Basu’s think aloud study and their Item 8d provide evidence of this misconception:

Students articulated that a loop repeats the same set of actions and expected loops to produce the exact same output in every iteration.

Value

How can you build on this misconception?

Students might think that the code before the loop executes, and then all iterations spawn off as independent (potentially parallel) continuations. This might be an opportunity to discuss sequential versus parallel computation.