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STRUCTUREDPROGRAMMING

C++ Operators

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Content2

C++ operators

Assignment operators

Arithmetic operators

Increment and decrement operators

Decision making operators (logical and relational)

Conditional operator

Precedence and associativity of operators

Common errors

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Objectives3

By the end you should be able to:

Use the assignments and arithmetic operators

How decisions are made in your programs

Write simple decisionmaking statements

Recognize the precedence and associatively of operators

Identify and use the C++ conditional operator (?:)

Identify and use Increment & decrement operators

Use operators in output statements

Properly mix data types in expression and calculations

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Operators

Data connectors within expression or equation

Concept related

Operand: data that operator connects and processes

Resultant: answer when operation is completed

Operators types based on their mission

Assignment

Arithmetic: addition, subtraction, modulo division, ...etc

Relational: equal to, less than, grater than, etc

Logical (decision-making): NOT, AND, OR

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Operators (cont.)

Operators types based on number of operands

Unary operators

Have only one operand

May be prefix or postfix

e.g. ++ !--

Binary operators

Have two operands

Infix

e.g. +&&==

Ternary operators

Have three operands

e.g. ? :

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Assignment operators

Assignment statement takes the form below

Binary operators

Expression is evaluated and its value is assigned to the variable on

the left side

Shorthand notation

varName = varName operator expression;

varName operator = expression;

6

varName = expression;

c = c + 3;

c += 3;

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Assignment operators (cont.)

Assignment between objects of the same type is always supported

7

Assignmentoperator

Sampleexpression

Explnation Assigns

Assume: int c = 3, d = 5, e = 4, f = 6, g = 12;

+= c += 7 c = c + 7 10 to c

-= d -= 4 d = d4 1 to d

*= e *= 5 e = e * 5 20 to e

/= f /= 3 f = f / 3 2 to f

%= g %= 9 g = g % 9 3 to g

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Arithmetic Operators

All of them are binary operators

Arithmetic expressions appear in straight-line form

Parentheses () are used to maintain priority of manipulation

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C++ operation C++ arithmeticoperator

Algebraicexpression

C++ expression

Addition + + 7 f + 7

Subtraction - p - c p - c

MUltiplication * bm or b . m b * m

Division / x / y or x y x / y

Modulus % r mod s r % s

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Arithmetic Operators

Precedence

Operators in parentheses evaluated first

Nested/embedded parentheses

Operators in innermost pair first

Multiplication, division, modulus applied next

Operators applied from left to right

Addition, subtraction applied last

Operators applied from left to right

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Example

The statement is written in algebra as

z = pr % q + w / (x y)

How can we write and evaluate the previous statement in C++ ?

z = p * r % q + w / (x - y);

10

53 42 16

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Increment and Decrement

Operators

Unary operators

Adding 1 to or (subtracting 1 from) variables value

Increment operator gives the same result of

(c=c+1) or (c+=1)

Decrement operator gives the same result of

(c=c-1) or (c-=1)

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Increment and Decrement Operators

(cont.)12

Operator Called Sample

expression

Explanation

++ Preincrement ++a Increment a by 1, then use the new value ofa in the expression in which a resides.

++ Postincrement a++ Use the current value of a in the expression

in which a resides, then increment a by 1.

Pridecrement --b Decrement b by 1, then use the new value of

b in the expression in which b resides.

Postdecrement b-- Use the current value of b in the expression

in which b resides, decrement b by 1.

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Examples13

int x = -10 , y;

y = ++x;

cout

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Relational and EqualityOperators

Binary operators

Used in decision -making statements

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Standard algebraic

equality operator orrelational operator

C++ equality

or relationaloperator

Example

of C++condition

Meaning of

C++ condition

Relational operators

> > x > y x is greater than y

< < x < y x is less than y

>= x >= y x is greater than or equal to y

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Relational and Equality Operators(cont.)

Have the same level of precedence

Applied from left to right

Used with conditions

Return the value true orfalse

Used only with a single condition

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Logical Operators

Used to combine between multiple conditions

&& (logical AND)

true if both conditions are true

gender == 1 && age >= 65

|| (logical OR)

true if either of condition is true

semesterAverage >= 90 || finalExam >= 90

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1st condition 2nd condition

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Logical Operators (cont.)

! (logical NOT, logical negation)

Returns true when its condition is false, and vice versa

!( grade == sentinelValue )

Also can be written as

grade != sentinelValue

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Conditional operator (?:)

Ternary operator requires three operands

Condition

Value when condition is true

Value when condition is false

Syntax

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Condition ?conditions true value :conditions false value

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Examples

Can be written as

Can be written as .. ?

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grade >= 60 ? cout

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Summary of Operator

Precedence and Associativity20

Operators Associativity Type

() [] left to right highest++ -- static_cast< type>( operand) left to right unary (postfix)++ -- + - ! & * right to left unary (prefix)* / % left to right multiplicative+ - left to right additive> left to right insertion/extraction< >= left to right relational== != left to right equality&& left to right logical AND|| left to right logical OR?: right to left conditional= += -= *= /= %= right to left assignment, left to right comma

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bool Variables in Expressions

false is zero and true is any non-zero

The following codes applies implicit conversion between bool and

int

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int x = -10 ;

bool flag = x ;

// true

int a = flag ;

// assign the value 1

int b = !flag;

// assign the value 0

x = flag + 3;

// assign the value 4

bool test1,test2,test3 ;

int x = 3 , y = 6 , z = 4 ;

test1 = x > y ; // false

test2 = !(x == y ); // true

test3 = x < y && x < z ; // true

test3 = test1 || test2 ; // true

test2 = !test1; // true

Code # 1 Code # 2

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Common Compilation Errors

Attempt to use % with non-integer operands

Spaces between pair of symbols e.g. (==, !=, etc)

Reversing order of pair of symbols e.g. =!

Confusing between equality (==) and assignment operator (=)

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Exercise - 123

What is the output of the following program?

1 #include

2

3 using std::cout;

4 using std::endl;

56 int main()

7 {

8 int x; int y; int z;

9

10 x = 30; y = 2; z = 0;

11

12 cout

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Exercise - 224

What is wrong with the following program?

1 int main()

2 {

3 int a,b,c,sum;

4 sum = a + b + c ;

5 return 0;

6 }

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Included Sections25

Chapter 2: from section 6 and 7

Chapter 4: section 11 and 12