Quiz Master II

Review — where we got to 5 min

• add [thing] to [questions v] puts a row on the end.
• (item (3) of [questions v]) reads a row back. Rows start at 1.
• (length of [questions v]) drives a loop of any size.

Quick-fire

Your list has 4 rows. What does (item (5) of [questions v]) give you?

Today’s Topic 3 min

• delete (1) of [questions v] — and what it does to the row numbers
• insert [thing] at (2) of [questions v] — pushing the rest down
• replace item (2) of [questions v] with [thing] — swapping in place
• delete all of [questions v] — starting over

Learning outcome

By the end of this lesson you will be able to:

1. Take a row out of a list and explain what happened to the rows below it.
2. Choose between insert and replace, and say why.
3. Build a game where the list is the state — what is left is what is left to do.

Learnt — taking things out and putting things in 28 min

1 · Delete, and the thing nobody expects

Variables has a block that takes one row out:

delete (1) of [questions v]
            

Here is the part that catches everybody. The list does not leave a gap — everything below moves up a row. So the question that was item 2 a second ago is item 1 now, and the numbers you were holding in your head are all wrong.

2 · Insert pushes the rest down

insert [BONUS: how many days in a week?] at (2) of [questions v]
            

3 · Replace swaps one row

replace item (1) of [questions v] with [What colour is a lemon?]
            

4 · Delete all, and starting again

You met this one last lesson as the block that stops your quiz doubling in size. It is also how you start a second game without pressing the green flag:

when [r v] key pressed
delete all of [questions v]
add [What colour is a banana?] to [questions v]
add [How many legs has a spider?] to [questions v]
            

Basic — the ones you get right leave 24 min

Open your quiz. You are going to change what the list means: from “all the questions” to “the questions you still have not got right”.

Step 1 — always ask row 1

1. Find your loop and take the counter out of it.
2. Change the say to (item (1) of [questions v]).
3. Run it. It asks the same question for ever — that is expected.

Step 2 — a right answer removes it

1. After the question, add ask [Your answer?] and wait.
2. In the right-answer half, add delete (1) of [questions v].
3. In the wrong half, do nothing to the list.

Step 3 — a wrong answer sends it to the back

1. In the wrong half, add the question to the end with add (item (1) of [questions v]) to [questions v].
2. Then delete (1) of [questions v].
3. Now a missed question comes round again, at the back of the queue.

Step 4 — stop when the box is empty

1. Wrap the lot in repeat until <(length of [questions v]) = (0)>.
2. After it, say something triumphant.

Step 5 — show your working

1. Make sure the list box is ticked so it shows on the Stage.
2. Play a round and watch the rows disappear as you get them right.

repeat until <(length of [questions v]) = (0)>
  say (item (1) of [questions v]) for (1.5) seconds
  ask [Your answer?] and wait
  if <(answer) = (item (1) of [answers v])> then
    say [Right - that one is done.] for (1) seconds
    delete (1) of [questions v]
    delete (1) of [answers v]
  else
    say [Not quite. It will come round again.] for (1) seconds
  end
end
say [All of them, finally!] for (3) seconds
            

A bonus question, mid-game

Drop a surprise question in, without disturbing the ones already answered.

• After two questions, a bonus appears next in the queue.
• The questions still to come keep their order.
• The ones already done are not asked again.

Fix the typo

One of your questions has a spelling mistake. Fix it without restarting the quiz.

• Find the row with the typo in it.
• Correct it in place.
• The list is the same length afterwards, and nothing moved.

replace item (4) of [questions v] with [What do cows drink?]
            

Play again

Let the player start a fresh game without touching the green flag.

• R empties the list and stocks it up again.
• A counter says which game this is.
• The old questions do not come back twice over.

when [r v] key pressed
change [plays v] by (1)
delete all of [questions v]
add [What colour is a banana?] to [questions v]
add [How many legs has a spider?] to [questions v]
say (join [Game ] (join (plays) [. All five back.])) for (2.5) seconds
            

Your own revision list

Build a second list as you play, holding only the questions you got wrong. At the end, that list is the thing worth keeping.

• A list called missed, emptied at the start.
• A wrong answer adds that question to it.
• At the end, the host says how many there are to revise.

when flag clicked
delete all of [missed v]
...
else
  say [Missed that one.] for (1) seconds
  add (item (n) of [questions v]) to [missed v]
end
            

Summary 5 min

• delete (1) of [questions v] takes a row out — and everything below it moves up.
• insert [q] at (2) of [questions v] pushes the rest down and makes the list longer.
• replace item (2) of [questions v] with [q] swaps one row and changes nothing else.
• delete all of [questions v] empties it, ready to stock again.
• A list can BE the game state: what is left in the box is what is left to do.

Delete

Take one row out. The rows below move up.

Insert

Put a row in at a given number. The rows below move down.

Replace

Swap what is in one row, leaving the length alone.

Queue

A list you always take from the front and add to the back.

Hand in

Save your quiz. Next lesson it stops needing the answer spelled exactly one way — one block will search a whole list of accepted answers for you.