Unit 2 On the AP Exam

2.1.1

AAP-1.B.2

would be written as

secretNumber ← 7

or

a white rounded rectangle containing the text 'secretNumber ← 7'

.

2.1.2

The code

ask (Why did the chicken cross the road?) and wait; set (user response) to (answer)

would be written as

DISPLAY("Why did the chicken cross the road?")
userResponse ← INPUT()

or

a white rounded rectangle containing two smaller white rounded rectangles: The first one contains first the word 'DISPLAY' in all caps and then a smaller white rectangle containing the quoted text 'Why did the chicken cross the road?'. The second one contains the text 'userResponse ← INPUT()'

.

AAP-3.A.8, AAP-3.A.9

Notice that the procedure

INPUT()

accepts the value from the user and returns that input value, which is then assigned to the variable

userResponse

with the

←

syntax. In Snap!, this is just like how answer accepts a value from the user and reports it, and that report is what the computer sets the variable user response to.

2.1.4

(which means set(score) to (score+1)

) would be written as

score ← score + 1

or

.

2.1.5

AAP-2.N.1 bullet 1

The list expression item (2) of (costumes)

would be written as

costumes[2]

or

. All three versions of this code would report/return the penguin costume (if only the AP language had costumes as a data type):
item (2) of (costumes) reporting a picture of the penguin costume

item (2) of (costumes) reporting a picture of the penguin costume

2.1.5

AAP-2.N.1 bullet 7

The expression length of (words list)

would be written as

LENGTH(wordsList)

or

.

2.2.1

AAP-1.C.1 second sentence, AAP-1.D.7

The list expression list{Señora, Ms. C, my cat, Hannah, Jake}

would be written as

[Señora, Ms. C, my cat, Hannah, Jake]

. The items are positioned in the list in the order they appear in the text: "Señora" has index 1, "Ms. C" has index 2, and so on.

2.2.1

AAP-1.D.7 bullet 2

The assignment instruction

would be written as

shoppingList ← []

or

.

AAP-1.D.7 bullet 1

The assignment instruction set (shopping list) to {apples, bread, carrots, rice, pasta}

would be written as

shoppingList ← [apples, bread, carrots, rice, pasta]

or

shoppingList ← [apples, bread, carrots, rice, pasta]

. (In this app, you'll want the shopping list to begin empty, and then the user will add or insert additional grocery items one at a time.)

2.2.1

AAP-2.N.1 bullet 4

insert (tomatoes) at (2) of (shopping list)

would be written as

INSERT(shoppingList, 2, "tomatoes")

or

.

AAP-2.N.1 bullet 5

would be written as

APPEND(shoppingList, "tomatoes")

or

.

2.2.1

AAP-2.N.1 bullet 6

would be written as

REMOVE(shoppingList, 2)

or

.

2.2.1

The items in a list are values, so you can use item of anywhere you can use any other expression. For example:

AAP-2.N.1 bullets 2 and 3

You can assign a list item to a variable. On the exam...
- would be written as
```
myFavoriteFood ← shoppingList[3]
```
  or
You can assign any value to a list item (a number, a string, a sprite, a costume, a script, another list, etc.). On the exam...
- would be written as
```
shoppingList[2] ← yourFavoriteFood
```
  or .
- would be written as
```
shoppingList[1] ← shoppingList[3]
```
  or .

2.2.1

When you run this script in Snap!, the second line of code assigns to shopping list 2 the value of shopping list (that is, the same list, not a copy). So, the third line of code modifies both variables:
set(shopping list) to (list(apple)(banana))
set(shopping list 2) to (shopping list)
add (carrot) to (shopping list) shopping list watcher showing the contents of the variable to be apple, banana, carrot; and the shopping list 2 watcher showing the contents of the variable to be apple, banana, carrot

AAP-1.D.7 bullet 3, AAP-2.N.2

However on the exam, the statement

shoppingList2 ← shoppingList

makes a copy of the list. So modifying one of them does not modify the other.

The rules for how to use lists and how they behave differ depending on the programming language you are using.

2.2.3

AAP-2.O.3

The procedure

goto()

isn't built in to the AP's language so it is written in lower case like other programmer-defined procedures.

The script for each (point) of (my drawing) (go to (point))

would be written as

FOR EACH point IN myDrawing
{
    goto(point)
}

or

FOR EACH point IN myDrawing
{
goto(point)
}

.

2.3.1

AAP-2.E.2

You may see these five relational operators:

=, >, <, ≥, ≤

as well as a sixth:

≠

, which means "not-equal" and reports false if the two inputs are equal and otherwise reports true (if they are not equal). When you write the () not equal ()

block, it will work like this:
(3) not equal (4) reporting true

These six relational operators all report a Boolean value (true or false).

2.3.2

AAP-2.F.1

The

,

, and

blocks will appear as

AND

,

OR

, and

NOT

and will work exactly the same way as they do in Snap!.

2.4.1

Different programming languages have different ways of handling negative inputs to the mod function. So you won't see any negative numbers used with mod on the exam.

The mod operator: The expression (17) mod (5)

would be written as

17 MOD 5

on the exam. If you see an expression with variables as input to mod, such as

a MOD b

, you can assume that a is zero or positive, and b is strictly positive (because you can't divide by 0).

AAP-2.B.5, AAP-2.C.1, AAP-2.C.2, AAP-2.C.3, AAP-2.C.4

On the exam, you may see these four arithmetic operators:

,

(plus, minus, times, divide) as well as

MOD

. Arithmetic operators are part of most programming languages. (Most text languages use

rather than

×

for multiplication because

×

isn't on most keyboards, and because it looks too much like the letter x.)

AAP-2.L.2

Order of operations: In a block language, the nesting of blocks determines the order of operations. For example, in 3 × (5 + 4)

you can see that the + block is an input to the × block, so the expression means 3×(5+4). Similarly, (3 × 5) + 4

means (3×5)+4. In Snap!, it's as if there are parentheses around every operation. But in text languages, you can write

3 * 4 + 5

without parentheses, so they need the rules you learn in math class (multiplication before addition, and so on). The mod operator is like multiplication and division; it happens before addition and subtraction. So for example,

7 + 5 MOD 2 - 6

means

7 + 1 - 6

, which is, of course, 2.

2.4.1

AAP-2.H.2

The procedures

move()

and

turn_clockwise()

aren't built in to the AP's language so they are written in lower case like other programmer-defined procedures.

The conditional expression if (size > 15) {repeat (4) {move (size) steps, turn clockwise (90) degrees}}

would be written as

IF(size > 15)
{
    REPEAT 4 TIMES
    {
        move(size)
        turn_clockwise(90)
    }
}

or

IF(size > 15)
{
REPEAT 4 TIMES
{
move(size)
turn clockwise(90)
}
}

As in Snap!, if the condition (size) > 15 is true, the code inside the if statement runs; if the condition is false, the code does not run.

2.4.3

AAP-3.C.2

You saw the procedure definition for a command in Unit 1 Lab 3 Page 4: Modify Your Pinwheel.

The definition for a reporter looks much like the definition for a command except that it includes a

RETURN

(like report). For example, this definition

In many languages (including Snap!) variables must be declared in some way (in Snap!, you can click the "Make a variable" button or use the script variables block). But the AP's language doesn't include variable declarations, so you won't see them on the exam.

square roots of (number) {script variables (positive root), set (positive root) to ((sqrt) of (number))), report (list (positive root) ((-1) × positive root))

would be written as

PROCEDURE squareRoots(number)
{
    positiveRoot ← sqrt(number)
    RETURN([positiveRoot, -1 * positiveRoot])
}

or

square roots of (number) {script variables (positive root), set (positive root) to ((sqrt) of (number))), report (list (positive root) (() - positive root))

AAP-3.A.7

As with report in Snap!, when a

RETURN

statement is executed, the flow of control returns to the place in your code where the procedure was called, and the procedure returns the value of the expression inside the

RETURN

command or report block.

Also, the procedure

sqrt

isn't built in to the AP's language so it is written in lower case like other programmer-defined procedures.

2.4.3

AAP-2.H.3

The conditional expression if (a > b) {
report true
} else {
report (a = b)
}

would be written as

IF(a > b)
{
    RETURN(true)
}
ELSE
{
    RETURN(a = b)
}

or

IF(a > b)
{
RETURN(true)
}
ELSE
{
RETURN(a = b)
}

As in Snap!, if the condition

a > b

is true, the code in first block of statements runs; if it is false, the code in second block of statements runs.

Unit 2: Abstraction

Lab 1: Games

Lab 2: Making Lists

Lab 3: Making Decisions

Lab 4: Making Computers Do Math