Visual Basic operators
last modified October 18, 2023
In this part of the Visual Basic tutorial, we talk about operators.
An operator is a special symbol which indicates a certain process is carried out. Operators in programming languages are taken from mathematics. Programmers work with data. The operators are used to process data.
We have several types of operators:
- Arithmetic operators
- Boolean operators
- Relational operators
- Bitwise operators
An operator may have one or two operands. An operand is one of the inputs (arguments) of an operator. Those operators that work with only one operand are called unary operators. Those who work with two operands are called binary operators.
Option Strict On Module Example Sub Main() Console.WriteLine(2) Console.WriteLine(-2) Console.WriteLine(2+2) Console.WriteLine(2-2) End Sub End Module
The + and - signs can be addition and subtraction operators as well as unary sign operators. It depends on the situation.
Option Strict On Module Example Dim a As Byte Sub Main() a = 1 Console.WriteLine(-a) ' Prints -1 Console.WriteLine(-(-a)) ' Prints 1 End Sub End Module
The plus sign can be used to indicate that we have a positive number. But it is mostly not used. The minus sign changes the sign of a value.
Option Strict On Module Example Dim a As Byte Dim b As Byte Sub Main() a = 3 * 3 b = 2 + 2 Console.WriteLine(a) ' Prints 9 Console.WriteLine(b) ' Print 4 End Sub End Module
Multiplication and addition operators are examples of binary operators. They are used with two operands.
The assignment operator
The assignment operator =
assigns a value to a variable. A
variable
is a placeholder for a value. In mathematics, the
=
operator has a different meaning. In an equation, the
=
operator is an equality operator. The left side of the equation
is equal to the right one.
x = 1 Console.WriteLine(x) ' Prints 1
Here we assign a number to the x
variable.
x = x + 1 Console.WriteLine(x)
The previous expression does not make sense in mathematics. But it is legal in
programming. The expression adds 1 to the x
variable. The right
side is equal to 2 and 2 is assigned to x
.
3 = x
This code example results in syntax error. We cannot assign a value to a literal.
Arithmetic operators
The following is a table of arithmetic operators in Visual Basic.
Symbol | Name |
---|---|
+ | Addition |
- | Subtraction |
* | Multiplication |
/ | Division |
\ | Integer Division |
Mod | Modulo |
^ | Exponentiation |
The following example shows arithmetic operations.
Option Strict On Module Example Dim a As Byte Dim b As Byte Dim c As Byte Dim add As Byte Dim sb As Byte Dim mult As Byte Dim div As Byte Sub Main() a = 10 b = 11 c = 12 add = a + b + c sb = c - a mult = a * b div = CType(c / 3, Byte) Console.WriteLine(add) Console.WriteLine(sb) Console.WriteLine(mult) Console.WriteLine(div) End Sub End Module
In the preceding example, we use addition, subtraction, multiplication and division operations. This is all familiar from the mathematics.
$ dotnet run 33 2 110 4
Next we show the distinction between normal and integer division.
Option Strict On Module Example Dim a As Single = 5 Dim b As Single = 2 Dim c As Single Sub Main() c = 5 / 2 Console.WriteLine(c) c = 5 \ 2 Console.WriteLine(c) End Sub End Module
In the preceding example, we divide two numbers using normal and integer division operator. Visual Basic has two distinct operators for division.
Dim a As Single = 5
We use floating point data types.
c = 5 / 2 Console.WriteLine(c)
This is floating-point division.
c = 5 \ 2 Console.WriteLine(c)
This is integer division. The result of this operation is always and integer.
$ dotnet run 2.5 2
The last two operators that we mention are modulo operator and exponentiation operator.
Console.WriteLine(9 Mod 4) ' Prints 1
The Mod
operator is called the modulo operator. It finds the
remainder of division of one number by another. 9 Mod 4
, 9 modulo 4
is 1, because 4 goes into 9 twice with a remainder of 1. Modulo operator can be
handy for example when we want to check for prime numbers.
Finally, we mention exponentiation operator.
Console.WriteLine(9 ^ 2) ' Prints 81
9 ^ 2 = 9 * 9 = 81
Concatenating strings
In Visual Basic we have two operators for string concatenation. The plus
+
operator and the &
ampersand operator.
We can also use the String.Concat
method.
Option Strict On Module Example Sub Main() Console.WriteLine("Return " & "of " & "the king") Console.WriteLine("Return " + "of " + "the king") Console.WriteLine(String.Concat("Return ", "of ", "the king")) End Sub End Module
We join three strings.
$ dotnet run Return of the king Return of the king Return of the king
Boolean operators
In Visual Basic, we have the following logical operators. Boolean operators are also called logical.
Symbol | Name |
---|---|
And | logical conjunction |
AndAlso | short circuit And |
Or | logical inclusion |
OrElse | short circuit Or |
Xor | logical inclusion |
Not | negation |
Boolean operators are used to work with truth values.
Option Strict On Module Example Dim x As Byte = 3 Dim y As Byte = 8 Sub Main() Console.WriteLine(x = y) Console.WriteLine(y > x) If (y > x) Console.WriteLine("y is greater than x") End If End Sub End Module
Many expressions result in a boolean value. Boolean values are used in conditional statements.
Console.WriteLine(x = y) Console.WriteLine(y > x)
Relational operators always result in a Boolean value. These two lines print False and True.
If (y > x) Console.WriteLine("y is greater than x") End If
The body of the If
statement is executed only
if the condition inside the parentheses is met. The
x > y
returns True, so the message "y is greater than x"
is printed to the terminal.
Option Strict On Module Example Dim a As Boolean Dim b As Boolean Dim c As Boolean Dim d As Boolean Sub Main() a = (True And True) b = (True And False) c = (False And True) d = (False And False) Console.WriteLine(a) Console.WriteLine(b) Console.WriteLine(c) Console.WriteLine(d) End Sub End Module
Example shows the logical And
operator. It evaluates to True only
if both operands are True.
$ dotnet run True False False False
The logical Xor
operator evaluates to True, if exactly one of the
operands is True.
Option Strict On Module Example Dim a As Boolean Dim b As Boolean Dim c As Boolean Dim d As Boolean Sub Main a = (True Xor True) b = (True Xor False) c = (False Xor True) d = (False Xor False) Console.WriteLine(a) Console.WriteLine(b) Console.WriteLine(c) Console.WriteLine(d) End Sub End Module
The logical Xor
evaluates to False if both operands are True or
both False.
$ dotnet run False True True False
The logical Or
operator evaluates to True, if either of the
operands is True.
Option Strict On Module Example Sub Main() Dim a As Boolean = True Or True Dim b As Boolean = True Or False Dim c As Boolean = False Or True Dim d As Boolean = False Or False Console.WriteLine(a) Console.WriteLine(b) Console.WriteLine(c) Console.WriteLine(d) End Sub End Module
If one of the sides of the operator is True, the outcome of the operation is True.
$ dotnet run True True True False
The negation operator Not
makes True False and False True.
Option Strict On Module Example Sub Main() Console.WriteLine(Not True) Console.WriteLine(Not False) Console.WriteLine(Not (4 < 3)) End Sub End Module
The example shows the negation operator in action.
$ dotnet run False True True
AndAlso
, OrElse
operators are short circuit evaluated.
Short circuit evaluation means that the second argument is only
evaluated if the first argument does not suffice to determine the value of the
expression: when the first argument of And evaluates to false, the overall value
must be false; and when the first argument of Or evaluates to true, the overall
value must be true. Short circuit evaluation is used mainly to improve
performance.
An example may clarify this a bit more.
Option Strict On Module Example Sub Main() Console.WriteLine("Short circuit") If (one AndAlso two) Console.WriteLine("Pass") End If Console.WriteLine("#############") If (one And two) Console.WriteLine("Pass") End If End Sub Function one As Boolean Console.WriteLine("Inside one") Return False End Function Function two As Boolean Console.WriteLine("Inside two") Return True End Function End Module
We have two functions in the example. Functions, unlike subroutines, return values. This is the main difference between them.
If (one AndAlso two) Console.WriteLine("Pass") End If
The one function returns False. The short circuit AndAlso
does not evaluate the second function. It is not necessary. Once an operand is
False, the result of the logical conclusion is always False. Only "Inside one"
is printed to the console.
Console.WriteLine("#############") If (one And two) Console.WriteLine("Pass") End If
In the second case, we use the And
. In this case, both functions
are called. Even though it is not necessary for the result of the expression.
$ dotnet run Short circuit Inside one ############# Inside one Inside two
Relational Operators
Relational operators are used to compare values. These operators always result in a boolean value.
Symbol | Meaning |
---|---|
< | less than |
<= | less than or equal to |
> | greater than |
>= | greater than or equal to |
= | equal to |
<> | not equal to |
Is | compares references |
Relational operators are also called comparison operators.
Console.WriteLine(3 < 4) ' Prints True Console.WriteLine(3 = 4) ' Prints False Console.WriteLine(4 >= 3) ' Prints True
As we already mentioned, the relational operators return boolean values. Note
that in Visual Basic, the comparison operator is =
.
Notice that the relational operators are not limited to numbers. We can use them for other objects as well. Although they might not always be meaningful.
Option Strict On Module Example Sub Main() Console.WriteLine("six" = "six") ' Prints True ' Console.WriteLine("a" > 6) this would throw ' an exception Console.WriteLine("a" < "b") ' Prints True End Sub End Module
We can compare string objects too. Comparison operators in a string context compare the sorting order of the characters.
Console.WriteLine("a" < "b") ' Prints True
What exactly happens here? Computers do not know characters or strings. For them, everything is just a number. Characters are special numbers stored in specific tables. Like ASCII.
Option Strict On Module Example Sub Main() Console.WriteLine("a" < "b") Console.WriteLine("a is: {0}", Asc("a")) Console.WriteLine("b is: {0}", Asc("b")) End Sub End Module
Internally, the a and b characters are numbers. So when we compare two
characters, we compare their stored numbers. The built-in Asc
function returns the ASCII value of a single character.
$ dotnet run True a is: 97 b is: 98
In fact, we compare two numbers, 97 with 98.
Console.WriteLine("ab" > "aa") ' Prints True
Say we have a string with more characters. If the first characters are equal, we compare the next ones. In our case, the b character at the second position has a greater value than the a character. That is why "ab" string is greater than "aa" string. Comparing strings in such a way does not make much sense, of course. But it is technically possible.
Finally, we mention the Is
operator. The operator checks if two
object references refer to the same object. It does not perform value
comparisons.
Option Strict On Module Example Sub Main() Dim o1 As Object = New Object Dim o2 As Object = New Object Dim o3 As Object o3 = o2 Console.WriteLine(o1 Is o2) Console.WriteLine(o3 Is o2) End Sub End Module
We create three objects and compare them with the Is
operator.
Dim o1 As Object = New Object Dim o2 As Object = New Object
We declare and initialise two Object instances. The Object
class is a base class for all classes in the .NET framework. We describe it
later in more detail.
Dim o3 As Object
The third variable is only declared.
o3 = o2
The o3
now refers to the o2
object. They are two
references to the same object.
Console.WriteLine(o1 Is o2) Console.WriteLine(o3 Is o2)
In the first case, we get False. The o1
and o2
are two
different objects. In the second case, we get True. The o3
and o2
refer to the same object.
Bitwise operators
Decimal numbers are natural to humans. Binary numbers are native to computers. Binary, octal, decimal, or hexadecimal symbols are only notations of the same number. Bitwise operators work with bits of a binary number. Bitwise operators are seldom used in higher level languages like Visual Basic.
Symbol | Meaning |
---|---|
Not | bitwise negation |
Xor | bitwise exclusive or |
And | bitwise and |
Or | bitwise or |
The bitwise negation operator changes each 1 to 0 and 0 to 1.
Console.WriteLine(Not 7) ' Prints -8 Console.WriteLine(Not -8) ' Prints 7
The operator reverts all bits of a number 7. One of the bits also determines, whether the number is negative or not. If we negate all the bits one more time, we get number 7 again.
The bitwise and operator performs bit-by-bit comparison between two numbers. The result for a bit position is 1 only if both corresponding bits in the operands are 1.
00110 And 00011 = 00010
The first number is a binary notation of 6, the second is 3 and the result is 2.
Console.WriteLine(6 And 3) ' Prints 2 Console.WriteLine(3 And 6) ' Prints 2
The bitwise or operator performs bit-by-bit comparison between two numbers. The result for a bit position is 1 if either of the corresponding bits in the operands is 1.
00110 Or 00011 = 00111
The result is 00110
or decimal 7.
Console.WriteLine(6 Or 3) ' Prints 7 Console.WriteLine(3 Or 6) ' Prints 7
The bitwise exclusive or operator performs bit-by-bit comparison between two numbers. The result for a bit position is 1 if one or the other (but not both) of the corresponding bits in the operands is 1.
00110 Xor 00011 = 00101
The result is 00101
or decimal 5.
Console.WriteLine(6 Xor 3) ' Prints 5
Compound assignment operators
The compound assignment operators consist of two operators. They are shorthand operators.
Option Strict On Module Example Dim a As Integer Sub Main a = 1 a = a + 1 Console.WriteLine(a) ' Prints 2 a += 1 Console.WriteLine(a) ' Prints 3 End Sub End Module
The +=
compound operator is one of these shorthand operators.
They are less readable than the full expressions but
experienced programmers often use them.
Other compound operators are:
-= *= \= /= &= ^=
Operator precedence
The operator precedence tells us which operators are evaluated first. The precedence level is necessary to avoid ambiguity in expressions.
What is the outcome of the following expression, 28 or 40?
3 + 5 * 5
Like in mathematics, the multiplication operator has a higher precedence than addition operator. So the outcome is 28.
(3 + 5) * 5
To change the order of evaluation, we can use parentheses. Expressions inside parentheses are always evaluated first.
The following list shows common Visual Basic operators ordered by precedence (highest precedence first):
Operator(s) | Description |
---|---|
^ |
exponentiation |
+ - |
unary identity and negation |
* / |
multiplication, float division |
\ |
integer division |
Mod |
modulus |
+ - |
addition, subtraction, string concatenation |
& |
string concatenation |
<< >> |
arithmetic bit shift |
= <> < > >= <= Is IsNot Like TypeOf Is |
All comparison operators |
Not |
negation |
And AndAlso |
conjunction |
Or OrElse |
Inclusive disjunction |
Xor |
Exclusive disjunction |
Operators on the same line in the list have the same precedence.
Option Strict On Module Example Sub Main() Console.WriteLine(3 + 5 * 5) Console.WriteLine((3 + 5) * 5) Console.WriteLine(Not True Or True) Console.WriteLine(Not (True Or True)) End Sub End Module
In this code example, we show some common expressions. The outcome of each expression is dependent on the precedence level.
Console.WriteLine(3 + 5 * 5)
This line prints 28. The multiplication operator has a higher precedence than
addition. First the product of 5*5
is calculated. Then 3 is added.
Console.WriteLine(Not True Or True)
In this case, the negation operator has a higher precedence. First, the first True value is negated to False, than the Or operator combines False and True, which gives True in the end.
$ dotnet run 28 40 True False
Associativity
Sometimes the precedence is not satisfactory to determine the outcome of an expression. There is another rule called associativity. The associativity of operators determines the order of evaluation of operators with the same precedence level.
9 / 3 * 3
What is the outcome of this expression? 9 or 1? The multiplication, deletion and
the modulo operator are left to right associated. So the expression is evaluated
this way: (9 / 3) * 3
and the result is 9.
Arithmetic, boolean, relational and bitwise operators are all left o right associated.
On the other hand, the assignment operator is right associated.
a = b = c = d = 0 Console.WriteLine("{0} {1} {2} {3}", a, b, c, d) ' Prints 0 0 0 0
If the association was left to right, the previous expression would not be possible.
The compound assignment operators are right to left associated.
j = 0 j *= 3 + 1 Console.WriteLine(j)
You might expect the result to be 1. But the actual result is 0. Because of the associativity. The expression on the right is evaluated first and than the compound assignment operator is applied.
AddressOf operator
The AddressOf
operator creates a function delegate that points to
another function. Delegates are type safe function pointers, they are used to
call methods of other objects.
Option Strict On Module Example Delegate Sub Display Dim msg As New Display(AddressOf Message1) Sub Main() msg.Invoke() msg = New Display(AddressOf Message2) msg.Invoke() End Sub Sub Message1() Console.WriteLine("This is message 1") End Sub Sub Message2() Console.WriteLine("This is message 2") End Sub End Module
In the code example, we use the AddressOf
operator to point to two
different subroutines.
Delegate Sub Display
We need to declare a delegate.
Dim msg As New Display(AddressOf Message1)
The delegate takes the address of a subroutine using the AddressOf
operator. Now we have a type-safe pointer to the Message1
subroutine.
msg.Invoke()
The Invoke
method calls the method, to which the delegate points.
msg = New Display(AddressOf Message2) msg.Invoke()
Now we give the delegate an address of another subroutine.
$ dotnet run This is message 1 This is message 2
Both messages are printed to the console.
In this part of the Visual Basic tutorial, we covered the operators.