Introduction to Logical Operations
This section provides a quick introduction of logical operations supported by VBScript: logical negation - Not, conjunction - And, disjunction - Or, exclusion - Xor, equivalence - Eqv, implication - Imp.
Logical operations are operations that:
- Operates on one Boolean operand or two Boolean operands.
- Produces a Boolean value by applying the logical operation specified by the operator.
There are 6 logical operations supported in VBScript:
- Logical Conjunction (And): Resulting (True) if and only if both operands are (True).
- Logical Disjunction (Or): Resulting (True) if one of operands is (True).
- Logical Negation (Not): Resulting (True) if the operand is (False).
- Logical Exclusion (Xor): Resulting (True) if and only if one of operands is (True).
- Logical Equivalence (Eqv): Resulting (True) if and only if both operands have the same value.
- Logical Implication (Imp): Resulting (True) if the second operand is (True) or both operands are (False).
To show you how logical operations work, I wrote the following script, logical_operation.html:
- Copyright (c) 1998 HerongYang.com. All Rights Reserved.
document.writeln(True And True)
document.writeln(True Or True)
document.writeln(True Xor True)
document.writeln(True Eqv False)
document.writeln(True Imp False)
Here is the output of this VBScript example script:
No surprises in the output. But logical equivalence operation and logical implication operation
are not commonly used operations.
Table of Contents
About This Book
Introduction of VBScript - Visual Basic Scripting Edition
Variant Data Type, Subtypes, and Literals
►Numeric Comparison Operations and Logical Operations
Introduction to Numeric Comparison Operations
►Introduction to Logical Operations
String Operations - Concatenation and Comparison
Variable Declaration and Assignment Statement
Expression and Order of Operation Precedence
Statement Syntax and Statement Types
Array Data Type and Related Statements
Array References and Array Assignment Statements
Conditional Statements - "If ... Then" and "Select Case"
Loop Statements - "For", "While", and "Do"
"Function" and "Sub" Procedures
Inspecting Variables Received in Procedures
Error Handling Flag and the "Err" Object
Regular Expression Pattern Match and Replacement
scrrun.dll - Scripting Runtime DLL Library
Creating Your Own Classes
IE Web Browser Supporting VBScript
IIS ASP Server Supporting VBScript
WSH (Windows Script Host)
Full Version in PDF/EPUB