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Logical Operators (Cross Ref > Operators)

Logical Operators

Languages Focus

Logical operators perform conditional and, or, and not operations. Some languages support both binary logical operators that link two and unary logical operators negate (make opposite) the truth value of its argument. Finally, some languages short circuit logic. For example, with this or that, if this is an expression returning true, then that is never executed.

Access VBA: and, or, not

Same as VB. Access VBA logical operators:

and	and, as in this and that
or	or, as in this or that
Not	Not, as in Not This

Access VBA never short circuits. Given the expression this or that as well as this and that, if this evaluates to false, then that is still executed.

Syntax Example:

'Given expressions a, b, c, and d:

If Not (a and b) and (c or d) Then

  'Do something.

End If

Access VBA Logical Operators (and, or, not) 2 certification questions.

Using the Logical Not Operator

You can use the not operator in many contexts. One of my favorite uses for it is to toggle boolean properities with a single line of code:

BooleanProperty = Not BooleanProperty

MS Access 2003 Working Demo

The following demo uses the not operator to toggle the visible property of a Image object from a button.

Create a new form and place a button and a Image on it. Add a picture to the Image with the Picture property.
Edit the Click event of the button and alter it as follows below. Select the button and edit the On Click event on the Event tab of the Properities explorer. Your Image object should be named Image1, but if it's not, use the correct object name.

Private Sub Command1_Click()
Image1.Visible = Not Image1.Visible
End Sub
Run the form and test. Select View | Form View and click the button. You'll notice the picture toggles between visible and not visible with a single line of code.

Access VBA Short Circuting Example:

In the following example, if Access VBA supported short circuting, the That function would never execute.

Function This()
    MsgBox ("The This function executed.")
    This = False
End Function

Function That()
    MsgBox ("The That function executed!")
    That = True
End Function

Private Sub Command0_Click()
    'Notice both the This and That functions execute
    'even though the This Function returned False.
    If This And That Then
        MsgBox ("hi")
    End If
End Sub

Linked Certification Question(s)

The following are practice certification questions with answers highlighted. These questions were prepared by Mike Prestwood and are intended to stress an important aspect of this KB post. All our practice questions are intended to prepare you generally for passing any certification test as well as prepare you for professional work.

Beginner

1 Beginner Level Question

Question #1: True or False?

Given the following code, which MsgBox will display? The True or the False one?

Dim a, b, c, d As Boolean
   
a = True
b = True
c = True
d = False
  
If Not (a And b) And (c Or d) Then
  MsgBox ("True")
Else
  MsgBox ("False")
End If

Answer:

True

False

Intermediate

1 Intermediate Level Question

Question #2: Yes or No?

Given the following two functions:

Function This()
    This = False
End Function

Function That()
    That = True
End Function

Will the That function in the following code execute?

Private Sub Command0_Click()
    If This And That Then
        MsgBox ("hi")
    End If
End Sub

Answer:

Yes

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

Code:

Access VBA Logical Operators (and, or, not)

ASP Classic: and, or, not

Same as VB. ASP Classic logical operators:

and	and, as in this and that
or	or, as in this or that
Not	Not, as in Not This

ASP Classic never short circuits. Given the expression this or that as well as this and that, if this evaluates to false, then that is still executed.

Syntax Example:

'Given expressions a, b, c, and d:

If Not (a and b) and (c or d) Then

  'Do something.

End If

ASP Classic Logical Operators (and, or, not) 2 certification questions.

ASP Classic Short Circuting Example:

In the following example, if ASP Classic supported short circuting, the That function would never execute. It's interesting to note that VB.Net has introduced two new operators to support short cicuiting: AndAlso and OrElse for use when you code in ASP.Net.

<%@LANGUAGE='VbScript'%>
<%Option Explicit%>

<html>

<body>
<h1>Short Circuting</h1>
<%
Function This()
    Response.Write("<br>The This function executed.")
    This = False
End Function

Function That()
    Response.Write("<br>The That function executed!")
    That = True
End Function

'Notice both the This and That functions execute
'even though the This Function returned False.
If This And That Then
  Response.Write("<br>Both are true.")
End If
%>
</body>

</html>

Linked Certification Question(s)

Beginner

1 Beginner Level Question

Question #1: True or False?

Given the following code, will True or False be written?

Dim a, b, c, d
  
a = True
b = True
c = True
d = False  
  
If Not (a And b) And (c Or d) Then
  Response.Write("True")
Else
  Response.Write("False")
End If

Answer:

True

False

Intermediate

1 Intermediate Level Question

Question #2: Yes or No?

Given the following two functions:

Function This()
    This = False
End Function

Function That()
    That = True
End Function

Will the That function in the following code execute?

If This And That Then
  Response.Write("<br>hello.")
End If

Answer:

Yes

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

Code:

ASP Classic Logical Operators (and, or, not)

C#:

Same as C++ and Java. C# logical operators:

&	and, as in this and that	No Short Circuit
&&	and, as in this and that	short circuits
\|	or, as in this or that	No Short Circuit
\|\|	or, as in this or that	short circuits
!	Not, as in Not This
^	either or, as in this or that but not both

Syntax Example:

//Given expressions a, b, c, and d:

if !((a && b) && (c || d))

  //Do something.

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

C++:

C++ logical operators:

&&	and, as in this and that
\|\|	or, as in this or that
!	Not, as in Not This
^	either or, as in this or that but not both

Syntax Example:

//Given expressions a, b, c, and d:

if !((a && b) && (c || d)) {

  //Do something.

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

C++/CLI:

Same as C++ and Java. C# logical operators:

&	and, as in this and that	No Short Circuit
&&	and, as in this and that	short circuits
\|	or, as in this or that	No Short Circuit
\|\|	or, as in this or that	short circuits
!	Not, as in Not This
^	either or, as in this or that but not both

Syntax Example:

//Given expressions a, b, c, and d:

if !((a && b) && (c || d)) {

  //Do something.

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

Corel Paradox:

ObjectPAL logical operators:

and	and, as in this and that
or	or, as in this or that
Not	Not, as in Not This

Like VBA, ObjectPAL never short circuits. Given the expression this or that as well as this and that, if this evaluates to false, then that is still executed.

Syntax Example:

;Given expressions a, b, c, and d:

if Not (a and b) and (c or d) then

  ;Do something.

endIf

ObjectPAL Logical Operators 1 certification question.

Simple Short Circuit Code Test

The following code snippet allows you to test out ObjectPAL's short circuiting. In the if statement of the pushButton event, the That() custom procedure executes even if This() is False.

To use the code, alter a pushButton event of a button as follows:

;This custom procedure.

proc This() Logical
   msgInfo("", "This")
   return False
endProc

;That custom procedure.

proc That() Logical
   msgInfo("", "That")
   return True
endProc

method pushButton(var eventInfo Event)

   ;Object always short circuits.

   ;The That() custom procedure executes even

   ;though This() returns false.
   if This() and That() then
     msgInfo("", "both are true")
   endIf
endMethod

Using the Logical Not Operator

You can use the not operator in many contexts. One of my favorite uses for it is to toggle boolean properities with a single line of code:

BooleanProperty = Not BooleanProperty

Working Paradox Demo

The following demo works in all versions of Paradox for Windows. The demo uses the not operator to toggle the visible property of a box from a button.

Create a new form and place a button and a box on it.
Name the box "TheBox". To rename it, select the box, right click and click properties. In the Name of object field, change the name to MyBox.
Edit the pushButton event and alter it as follows below. Select the button, right click, click Object Explorer. Double click the pushButton event on the Events tab.

method pushButton(var eventInfo Event)
TheBox.Visible = Not TheBox.Visible
endMethod
Run the form and test. Select Program | Run and click the button. You'll notice the visible box toggles between visible and not visible with a single line of code.

Linked Certification Question(s)

Beginner

1 Beginner Level Question

Question #1: Multiple Choice

What are the logical operators?

Answer:

and
andAlso
or
orElse
not

and
andAlso
or
orElse
not
xor

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

Code:

ObjectPAL Logical Operators

Delphi:

Delphi logical operators:

and	and, as in this and that
or	or, as in this or that
not	Not, as in Not This
xor	either or, as in this or that but not both

The Delphi compiler default is to short circuit multi argument boolean expressions when the result is known before the evaluation completes. To disable short circuiting, use the {$B+} compiler directive. To reset it back to the compiler default of short circuting, use the {$B-} compiler directive.

Syntax Example:

//Given expressions a, b, c, and d:

if Not (a and b) and (c or d) then

  //Do something.

Delphi Logical Operators 1 certification question.

Using the Logical Not Operator

You can use the not operator in many contexts. One of my favorite uses for it is to toggle boolean properities with a single line of code:

BooleanProperty = Not BooleanProperty;

For example, if you have an Image control on a form you can toggle it's visibility with a single line of code:

Image1.Visible := Not Image1.Visible;

Linked Certification Question(s)

Beginner

1 Beginner Level Question

Question #1: True or False?

Given the following code, which ShowMessage will display? The True or the False one?

var
  a, b, c, d: Boolean;
begin
  a := True;
  b := True;
  c := True;
  d := True;

  if Not (a and b) and (c or d) then
    ShowMessage('True')
  else
    ShowMessage('False');
end;

Answer:

True

False

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

Code:

Delphi Logical Operators

Delphi Prism:

Prism logical operators:

and	and, as in this and that
or	or, as in this or that
not	Not, as in Not This
xor	either or, as in this or that but not both

Syntax Example:

//Given expressions a, b, c, and d:

if Not (a and b) and (c or d) then

  //Do something.

Linked Certification Question(s)

Beginner

1 Beginner Level Question

Question #1: True or False?

Given the following code, which MessageBox.Show will display? The True or the False one?

var a, b, c, d: Boolean;

a := False;
b := False; 
c := True; 
d := False;
  
if Not (a and b) and (c or d) then 
  MessageBox.Show('True') 
else 
  MessageBox.Show('False');

Answer:

True

False

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

Java:

Java logical operators:

&&	and, as in this and that
\|\|	or, as in this or that
!	Not, as in Not This
&	boolean logical OR (not short circuited)
\|	boolean logical OR (not short circuited)
?:	Ternary (short for if-then-else)
~	Unary bitwise complement
<<	Signed left shift
>>	Signed right shift
>>>	Unsigned right shift
^	Bitwise exclusiv OR

Syntax Example:

//Given expressions a, b, c, and d:

if !((a && b) && (c || d)) {

  //Do something.

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

JavaScript:

JavaScript logical operators:

&&	and, as in this and that
\|\|	or, as in this or that
!	Not, as in Not This

JavaScript always short circuits. Given the expression this || that, if this evaluates to true, then that is never executed.

Syntax Example:

//Given expressions a, b, c, and d:

if !((a && b) && (c || d)) {

  //Do something.

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

Perl:

Perl logical operators:

&& or and	and, as in this and that
\|\| or or	or, as in this or that
!	Not, as in Not This

Syntax Example:

#Given expressions a, b, c, and d:

if !((a && b) && (c || d)) {

  #Do something.

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

PHP: and, &&, or, ||, !, Xor

PHP logical operators:

and, &&	and, as in this and that
or, \|\|	or, as in this or that
!	Not, as in Not This
Xor	either or, as in this or that but not both

Syntax Example:

#Given expressions a, b, c, and d:

if !((a && b) && (c || d)) {

  #Do something.

};

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

VB Classic: and, or, not

VB Classic logical operators:

and	and, as in this and that
or	or, as in this or that
Not	Not, as in Not This

VB Classic never short circuits. Given the expression this or that as well as this and that, if this evaluates to false, then that is still executed.

Syntax Example:

'Given expressions a, b, c, and d:

If Not (a and b) and (c or d) Then

  'Do something.

End If

VB Classic Logical Operators (and, or, not) 2 certification questions.

Using the Logical Not Operator

You can use the not operator in many contexts. One of my favorite uses for it is to toggle boolean properities with a single line of code:

BooleanProperty = Not BooleanProperty

VB6 Working Demo

The following demo uses the not operator to toggle the visible property of a PictureBox from a button.

Create a new form and place a button and a PictureBox on it. Add a picture to the PictureBox with the Picture property.
Edit the Click event and alter it as follows below (double click the button). Your PictureBox should be named Picture1, but if it's not, use the correct object name.

Private Sub Command1_Click()
Picture1.Visible = Not Picture1.Visible
End Sub
Run the application and test. Select Run| Start and click the button. You'll notice the picture toggles between visible and not visible with a single line of code.

VB Classic Short Circuting Example:

In the following example, if VB Classic supported short circuting, the That function would never execute. It's interesting to note that VB.Net has introduced two new operators to support short cicuiting: AndAlso and OrElse but you'll have to move to VB.Net to take advantage of them.

Function This()
    MsgBox ("The This function executed.")
    This = False
End Function

Function That()
    MsgBox ("The That function executed!")
    That = True
End Function

Private Sub Command0_Click()
    'Notice both the This and That functions execute
    'even though the This Function returned False.
    If This And That Then
        MsgBox ("hi")
    End If
End Sub

Linked Certification Question(s)

Beginner

1 Beginner Level Question

Question #1: True or False?

Given the following code, which MsgBox will display? The True or the False one?

Dim a, b, c, d As Boolean
   
a = True
b = True
c = True
d = False
  
If Not (a And b) And (c Or d) Then
  MsgBox ("True")
Else
  MsgBox ("False")
End If

Answer:

True

False

Intermediate

1 Intermediate Level Question

Question #2: Yes or No?

Given the following two functions:

Function This()
    This = False
End Function

Function That()
    That = True
End Function

Will the That function in the following code execute?

Private Sub Command0_Click()
    If This And That Then
        MsgBox ("hi")
    End If
End Sub

Answer:

Yes

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages

Code:

VB Classic Logical Operators (and, or, not)

VB.Net:

VB.Net logical operators:

And	and, as in this and that	No Short Circuit
AndAlso	and, as in this and that	short circuits
Or	or, as in this or that	No Short Circuit
OrElse	or, as in this or that	short circuits
Not	Not, as in Not This
Xor	either or, as in this or that but not both

Syntax Example:

'Given expressions a, b, c, and d:

If Not (a and b) and (c or d) Then

  'Do something.

End If

Linked Certification Question(s)

Beginner

1 Beginner Level Question

Question #1: Multiple Choice

What are the logical operators?

Answer:

And
AndAlso
Or
OrElse
Not
XOR

More Info

To/From Code Guide: Logical Operators (Cross Ref > Operators) vs. Other Languages