Functions: Name a Group of Steps and Use It Again

Answer key

1. 1. It gives a name to a group of steps so you can run them again by writing the name.
   A function names a chunk of steps for reuse. Choosing steps only when a condition is true is an if–else, and counting passes is a loop's job. Speed does not change.
2. 2. F F L F F L
   Each call runs the whole body in order, so two calls give F F L, then F F L again. F F L is only one call, and F F F F L L changes the order of the steps.
3. 3. 4
   Each jump is 2 forward moves, and there are 2 calls: 4. R turns the robot but does not move it, so 5 counts the turn as a move, and 2 counts only one call.
4. 4. 0
   spin is defined but never called, so its turns never run. The program only runs F F. 4 assumes defining a function also runs it.
5. 5. stair stair stair
   The staircase has three steps, so stair is called three times. Two calls stop one step short, four calls run off the grid, and Repeat 3 [F L F] keeps turning left and never turns back to face right, so the robot runs off the left edge of the grid.
6. 6. 12
   Each call is 3 commands, and there are 4 calls: 3 × 4 = 12. 4 counts the calls, 7 adds 3 + 4, and 16 assumes 4 commands in each call.
7. 7. 5
   line(3) moves 3 squares and line(2) moves 2 more: 5. R only turns. 6 multiplies 3 × 2 instead of adding the two lines.
8. 8. line(5)
   From S to G is 5 moves, because the robot already stands on S. line(6) counts the squares instead of the moves and runs off the end; line(4) and line(2) line(2) stop one square short.
9. 9. 6, then 10
   Each call uses its own input: 3 + 3 = 6, then 5 + 5 = 10. 16 adds the inputs first, which the program never does, and 9, then 25 multiplies each number by itself instead of adding it to itself.
10. 10. line(2) R line(2)
    Two squares right, turn right to face down, then two squares down reaches G. line(3) hits the wall in the top row, L turns the robot up and off the grid, and turning first sends it into a wall below S.
11. 11. square
    Four sides with a right turn after each make a square that returns to the start. moveRight describes only the turns, fourSteps hides what happens, and a stair climbs instead of coming back.
12. 12. Change it to L L
    Turning around is a half turn, which is two quarter turns. R is still a quarter turn (the other way), L R turns left and then straight back, so the robot keeps its direction, and F L adds an extra move.
13. 13. 1
    Change the definition once and all 6 calls use the corrected steps. 6 treats each call like copied code, which is exactly the work a function saves.
14. 14. The body uses 3 instead of n, so the input is ignored.
    The fix is Repeat n [F], so the input decides the count. Calling line(3) hides the bug instead of fixing it, a loop can go inside a function, and five calls would move 15 squares.
15. 15. Reasons include: the program is shorter; it is easier to read because the name says what happens; and if the steps have a bug, you fix it in one place instead of every copy.
    Any two clear reasons are fine. The strongest answers mention fixing a bug once.
16. 16. 16 moves, back at the start facing right
    One square is 4 corners × 2 forward moves = 8, so two squares make 16. Each square has four right turns, a full turn, so the robot is back at the start facing right. 8 counts only one call of square.
17. 17. 3 squares right and 3 squares down
    Each zigzag moves 1 right, turns to face down, moves 1 down and turns back to face right. Three calls give 3 right and 3 down. R turns toward the bottom of the grid, not the top, and 6 right assumes every F moves right, ignoring the turns.
18. 18. Define step [F L F R]; then Repeat 4 [step] (or step step step step).
    Trace one call: right, turn up, up, turn back to face right. Ending each call facing right means the next call starts the same way. A different name is fine if it describes the steps.