VBScript Tutorials - Herong's Tutorial Notes
Dr. Herong Yang, Version 4.01

Variable Inspection and Numeric Conversion

Part:   1  2  3  

VB Script Tutorials - Herong's Tutorial Notes © Dr. Herong Yang

Data Types and Literals

Variables

Logic Operations

String Operations

Conditional Statements

Arrays

Loop Statements

Functions and Subroutines

Built-in Functions

Variable Inspection

... Table of Contents

(Continued from previous part...)

There are a number of interesting notes here:

  • Line V3 shows that (3.14) is reported as (Double). I was expecting Single.
  • Line V6 shows that (TRUE) is reported as (Num=Y). What number TRUE will be converted to?
  • Line S1 shows that ("777") is reported as (String) and (Num=Y). That is reasonable.
  • Line S2 shows that ("3.14") is reported as (String), (Num=Y) and (Date=Y). What date "3.14" will be converted to?
  • Line A3 shows that a dynamic-size array is not Empty even before calling ReDim to set its size.
  • Lines A1 to A5 show that arrays will never be Empty or Null.
  • Lines E1 to E2 show that Empty and Null are independent data types and data literals.
  • Line E2 shows that Empty is reported as (Num=Y). What number Empty will be converted to?
  • Line O1 shows that (document) is an object of "HTMLDocument" type. This object is created by IE and passed the IE VB script environment.

Parsing Long Integers

A common task of handling user input is to convert user entered data into a long integer. This sounds like an easy task. But not really, if you allow the user to type in anything. I have tried my best in the following example to convert the input data as much as possible into a long integer, parsing_integer.html: 

<html>
<body>
<!-- parsing_integer.html
   Copyright (c) 2006 by Dr. Herong Yang. http://www.herongyang.com/
-->
<pre>
<script language="vbscript">

   document.writeln(" ")
   document.writeln("Converting variants to integers:")
   document.writeln("   777 = " & GetInteger(777))
   document.writeln("   ""777"" = " & GetInteger("777"))
   document.writeln("   3.14159 = " & GetInteger(3.14159))
   document.writeln("   ""3.14159"" = " & GetInteger("3.14159"))
   document.writeln("   ""Hello"" = " & GetInteger("Hello"))
   document.writeln("   True = " & GetInteger(True))
   document.writeln("   Empty = " & GetInteger(Empty))
   document.writeln("   Null = " & GetInteger(Null))
   document.writeln("   ""1+2"" = " & GetInteger("1+2"))
   document.writeln("   777777 = " & GetInteger(777777))
   document.writeln("   3.3e200 = " & GetInteger(3.3e200))
   document.writeln("   ""3.3e20000"" = " & GetInteger("3.3e20000"))

Function GetInteger(vAnyThing)
   If IsNumeric(vAnyThing) Then
'      GetInteger = CInt(vAnyThing) 'Error 1: overflow on 777777
'      GetInteger = CLng(vAnyThing) 'Error 2: overflow on 3.3e200
      GetInteger = CDbl(vAnyThing)
      If Abs(GetInteger) < 2147483647 Then
         GetInteger = CLng(GetInteger)
      Else
         GetInteger = -2147483648
      End If
   Else
      GetInteger = -2147483648
   End If 
End Function
</script>
</pre>
</body>
</html>

Here is the output: 

Converting variants to integers:
   777 = 777
   "777" = 777
   3.14159 = 3
   "3.14159" = 3
   "Hello" = -2147483648
   True = -1
   Empty = 0
   Null = -2147483648
   "1+2" = -2147483648
   777777 = 777777
   3.3e200 = -2147483648
   "3.3e20000" = -2147483648

Note that:

  • I used IsNumeric() to filter out all other data that could not be converted into a number.
  • Then I used CDbl() to get the converted number.
  • Comments marked with "Error 1" and "Error 2" show that using "CInt()" or "CLng()" may result overflow error.
  • Converting a Double number to Long number is relatively easy as shown in my code.

Conclusions

  • "TypeName()" and "VarType()" are powerful tools to help you to determine the data structure and data type of any given variable.
  • "IsNumeric() and CDbl()" are also useful to convert any given variable to a number.

Part:   1  2  3  

Dr. Herong Yang, updated in 2006
VBScript Tutorials - Herong's Tutorial Notes - Variable Inspection and Numeric Conversion