revision expressions & constructs lesson...

Revision Expressions & constructs

Lesson 1

1. Selection/Conditional

2. Repetition

3. Linear

Name the common repetition constructs

1. Do While . . . Loop

2. Do . . . Until Loop

3. For . . . Next

Loop continues while condition is true

Do While RandomNum > 10 RandomNum = InputBox.Show(“Input random number”) Loop

Do RandomNum = InputBox.Show(“Input random number”) Loop While RandomNum > 10

Since condition is at end of loop, the loop body executes at least once.

Loop continues until condition is true

Do until RandomNum = 10 RandomNum = InputBox.Show(“Input random number”) Loop

Do RandomNum = InputBox.Show(“Input random number”) Loop until RandomNum = 10

Since condition is at end of loop, the loop body executes at least once.

Loop continues for specified number of repetitions

For x = 1 to 10 NewName = InputBox(“Enter name”) lstNames.Items.Add(NewName) Next x

if

Select . . . Case

One or more lines of code are executed depending upon a condition

IF x > 70 Then MsgBox(“Distinction”) ElseIF x > 60 Then MsgBox(“Merit”) ElseIF x > 50 Then MsgBox(“Pass”) Else MsgBox(“Fail”) End IF

The Else and Else IF sections is optional

Select . . Case construct allows a large number of results

Select Case Month Case 1 MsgBox(“Jan”) Case 2 MsgBox(“Feb”) Case 3 MsgBox(“Mar”) Case 4 MsgBox(“Apr”) Case 5 MsgBox(“May”) End Select

Mathematical equations

= 2 + 4/2 + 1

5

= 2 + 4 * 2

10 (not 12)

Precedence indicates when operators will be evaluated in complex expressions.

Operators with high precedence are evaluated before operators with low precedence.

For example, the multiplication operator (*) has higher preference than the addition operator (+), so the expression:

2+3*4

equals 14, not 20.

Order Operator Explanation

1 ^ Exponential

2 * Multiplication

3 / Integer division

4 \ Division

5 MOD Returns remainder of division

6 + Addition

7 - Subtraction

8 & or (+)

Concatenation

= 7 + 4*2 + 3

= 7 + 8 + 3

= 18

1st

= 16 / 4 * 2

= 16 / 8

= 2

Lets try some more

= 2 + 4 / 2

4

= 10-10*2-2

= 10-20-2

-12

=3+4+2—1

10

= 2 + 18 * 2

38

= 80 / 2 * 2

20

=4*4/2*2/4

1

=10/20+1*0.5

1

^ operator

This is an exponential mathematical operator

22 = 2 ^ 2 = 2 * 2 = 4

23 = 2 ^ 3 = 2 * 2 * 2 = 8

42 = 4 ^ 2 = 4 * 4 = 16

= 4 + 2 ^ 2 – 1

7

= 2 ^ 3 + 2

10 = (2*2*2+2)

x = 80 / 2 ^ 2

20

= 80/2*2/2^2

5

= 4*4/2*2*2*4

= 4^2/2^3*4

= 16 / 8 * 4

= 0.5

Parenthesis can help read in assembling an expression.

Parenthesis also make the expression easier to read.

Types of brackets include: ◦ round brackets ( )

◦ square brackets [ ]

◦ curly brackets - braces { }

◦ angle brackets 〈〉

2

yxt

t = ( + y) / 2

22

rt

t= 2 * ( r / 2 )

23

y

w

rt

t = (r / (3+w)) * (y / 2)

32

3py

t

t = ((y/2)^3) * (p/3)

242

h

p

yxt

t = + ((y / (2*p)) / h) * (4 ^ 2)

hey

tr

4

3

2

2

t = (((2*y)^(3*r)) / (2^4)) * (e-h)

er

eeeyxt

2

2

t = *((2+y) / 2)+((e^3/(r+e))

162

yxt

2

1

22 Hint:

t = +(y/2) – (16 ^ (1/2))

Constructs

Iteration

Expressions

Revision: Programming tasks