Operators and Expressions

Operators

are the symbols that represent a specific mathematical or logical processing in programming.

The following are some of the operators used in C#:

Arithmetic Operators

Logical Operators

Relational Operators

Assignment Operators

Arithmetic Operators

These are operators used in performing mathematical operations on numerical values.

Table 1 shows the basic arithmetic operators on C#.

Assume the following variable declarations:

int a = 11, b = 5;

Operator Description Example Return value

+

Adds two (2) operands

Example: a + b

Return value: 16

-

Subtracts the second operand from the first operand

Example: a – b

Return value: 6

*

Multiplies both operands

Example: a * b

Return value: 55

/

Divides the first operand by second operand

a / b

2

Table 1. C# arithmetic operators (Gaddis, 2016)

Relational Operators

These are used to determine the relationship between operands of numeric values and generate a decision on that base. These return Boolean values true and false.

Assume the following variable declarations:

int a = 11, b = 5;

>

Determines if the value of the first operand is greater than the value of the second operand—if yes, it returns true; otherwise, false. a > b true

<

Determines if the value of the first operand is less than the value of the second operand—if yes, it returns true; otherwise, false. a < b false

=

>=

Determines if the value of the first operand is greater than or equal to the value ofthe second operand—if yes, it returns true; otherwise, false. a >= b true

<=

Determines if the value of the first operand is less than or equal to the value of the second operand—if yes, it returns true; otherwise, false. a <= b false

==

Determines if the two (2) operands are equal or not—if the values are equal, it returns true; otherwise, false. a == b false

!=

Determines if the two (2) operands are equal or not—if the values are not equal, it returns true; otherwise, false.

a != b

true

Table 2. C# relational operators (Gaddis, 2016)

Logical Operators

These are operators used in performing logical operation. These operate on logical expressions and returns a Boolean value.

Table 3 shows the logical operators on C#.

Assume the following variable declarations:

bool A = true, B = false;

&& Logical AND operator

This returns true only if both operands are true; otherwise, false.

Example: A && B

Value: false

^ Logical XOR operator

This returns true if only one (1) operand is true; otherwise, false.

Example: A ^ B

Value: true

! Logical NOT operator.

This reverses the value of a Boolean variable. If the value of the Boolean variable is true, the NOT operator will make it false and vice versa.

Example: !A

Value: false

Assignment Operators

These are used to assign a value or the result of an expression to a variable.

Table 4 shows the assignment operators on C#.

Assume the following variable declarations:

int a = 2, b = 5;

=

This assigns a value of a variable or expression to the variable on its left side.

Example: b = a

Value: 2

+=

This adds left operand to the first operand and assigns the result to the first operand.

Example: b+=a

Value: 7

-=

This subtracts the second operand from the first operand and assigns the result to the first operand.

Example: b-=a

Value: 3

*=

This multiplies both operands and assigns the result to the first operand.

Example: b*=a

Value: 10

/=

This divides the first operand by the second operand and assigns the result to the first operand.

Example: b/=a

Value: 2

%=

This assigns the remainder result to the first operand after dividing the first operand by the second operand. Example: b%=a Value: 1

++

This adds 1 to the first operand and assigns the result to the first operand. Example: b++ Value: 6

--

This subtracts 1 from the first operand and assigns the result to the first operand. Example: b-- Value: 4

Table 4. C# assignment operators (Gaddis, 2016)

Expression

An __________in C# is a combination of operands (or variables) and operators that can be evaluated to a single value.

If all operands in an expression are integers, the expression evaluates to an integer value. For example: int x = 10 + 5 * 2; //evaluates to 20.

If an expression contains a floating-point value, it evaluates to a floating-point value. For example: double y = 10 + 5 * 2.0; //evaluates to 20.0.

Operator precedence and associativity

defines a set of rules indicating the order in which the operator should be evaluated in an expression.

When two (2) or more operators are used in an expression, the operators with the higher precedence are executed first, followed by the operators of lower precedence.

Table 5 displays common C# operators’ precedence and their associativity. The operators in the table are arranged in order of precedence from highest to lowest.

Precedence: Highest

Operators: !, ++, --, ()

Associativity: Left to right

Precedence: Intermediate 1

Operators: *, /, %

Associativity: Left to right

Precedence: Intermediate 2

Operators: +, -

Associativity: Left to right

Precedence: Intermediate 3

Operators: <, <=, >, >=

Associativity: Left to right

Precedence: Intermediate 4

Operators: ==, !=

Associativity: Left to right

Precedence: Intermediate 5

Operators: ^

Associativity: Left to right

Precedence: Intermediate 6

Operators: &&, ||

Associativity: Left to right

Precedence: Lowest

Operators: =, *=, /=, %=, +=, -=

Associativity: Right to left

Table 5. Common C# operators’ precedence and associativity (Harwani, 2015)

Consider the following expression:

int a = 2 + 3 * 4;

The precedence of the multiplication operator is higher than the plus operator, and the assignment operator has the lowest precedence. Therefore, 3 * 4 is evaluated first, and the result is added to 2.

When operators of the same precedence are used in a single expression, they are evaluated from left to right.

System.Math

The ___________ class includes several methods that perform a variety of calculations that can be used in a program.

Some of methods provided by Math class:

Pow()

Raises a number to the given power.

Exp()

Raises the constant e to the given power.

Log()

Returns the natural and 10-based logarithm, respectively.

Sqrt()

Returns the square root of the given number.

Sign()

Returns the sign of the specified number.

Abs()

Returns the absolute value of a given number.

Ceiling()

Returns the smallest integral value larger than or equal to a fractional number.

Floor()

Returns the largest integral value smaller than or equal to the given fractional number.

Round()

Returns the number after rounding it to the nearest integral value.

Truncate()

Returns the number after removing its fractional part.

Sin()

Returns the sine of the specified angle.

Cos()

Returns the cosine of the specified angle.

Tan()

Returns the tangent of the specified angle.

Table 6. C# Math class methods (Harwani, 2015)

static methods

The methods of Math class are ______________, which means they are used with the class name without instantiating an object.

For example:

double answer = Math.Pow(2, 3);

//returns 8

Operators

This specifies which operations to perform on operands

% Modulus operator

returns the remainder after dividing first operand by second operand

1

What is the output of

int result = 10 % 3; 
Console.WriteLine(result);

11

What is the result of

int result = 5 + 3 * 2;

True

What is the output of

Console.WriteLine(5 > 3);

False

Evaluate

bool result = (4 == 5);
Console.WriteLine(result);

False

What does

Console.WriteLine(true && false); 

output?

True

What is the result of

Console.WriteLine(true || false);

Given

int x = 5; 
x += 3;
Console.WriteLine(x);

what is the output?

20

What does

int y = 10; 
y *= 2;
Console.WriteLine(y); 

print?

4

What is the output of

int result = 10 - 2 * 3 + 4 / 2;

8

What does

Console.WriteLine(Math.Pow(2, 3)); 

output?

5

What is

Console.WriteLine(Math.Sqrt(25));

10

What does

Console.WriteLine(Math.Abs(-10)); 

print?

5

Evaluate

Console.WriteLine(Math.Ceiling(4.3));

4

Evaluate

Console.WriteLine(Math.Floor(4.9));

4

What is the result of

Console.WriteLine(Math.Round(4.5));

4

What does

Console.WriteLine(Math.Truncate(4.9)); 

print?

1

Compute

Console.WriteLine(Math.Sin(Math.PI / 2));

1

Compute

Console.WriteLine(Math.Cos(0));

1

Compute

Console.WriteLine(Math.Tan(Math.PI / 4));

-1

What does

Console.WriteLine(Math.Sign(-15)); 

return?

2.718281828459045

What is the output of

Console.WriteLine(Math.Exp(1));

2

Compute

Console.WriteLine(Math.Log(100, 10));

Math.Log(x, base) (Logarithm)

is the inverse of exponentiation.

It answers: "To what power must the base be raised to get x?"

Example:

Console.WriteLine(Math.Log(100, 10)); 

Output: 2

Explanation: Since 10^2 = 100, the logarithm of 100 with base 10 is 2.