Find the Dimensions of a Multidimensional Array

How to Use VBScript Ubound with an Unknown Number of Dimensions

Sep 22, 2009

VBScript Ubound d can be used to get the number of elements in a multidimensional array. However, the number of dimensions must be known. A simple function will help

VBScript (or Visual Basic script) handles arrays very well. A VBScript programmer can quickly and easily:

And VBScript is particularly useful for the programmer because it has a method for returning the maximum index number for an array. This method is called ubound, and this will even work with multidimensional arrays. However, there is a potential problem.

The number of dimensions is required by ubound but there is no method for calculating the number of dimensions in an array. Fortunately the VBScript programmer can write a function that will do the job. However, before doing that it is worth looking at simple and multidimensional arrays.

Working with a Simple Array in VBScript

The programmer creates a one dimensional array by defining its maximum index number:

Option Explicit

wscript.echo "A Simple Array...."

Dim name_array(2)

In this example the array will have three elements (with index number 0, 1 and 2), and the elements can be populated with data:

name_array(0) = "Fred"

name_array(1) = "Jane"

name_array(2) = "Mary"

If any more elements are written to then an error will occur, for example the following is illegal:

However, if the correct number of elements are populated then the programmer can use ubound to identify how many elements there are:

Dim i: For i = 0 To ubound(name_array)

wscript.echo name_array(i)

The result of this can be seen in figure 1 at the bottom of this article, and it's worth noting here that the default number of dimensions for ubound is one.

Working with a Multidimensional Arrays in VBScript

Multidimensional arrays are defined in a similar way to one dimensional arrays, and they require the maximum index number for each dimension:

apartments (0,0,0) = "Ground floor corner"

apartments (1,1,1) = "1st floor "

apartments (2,2,2) = "2nd floor far corner"

And again ubound can be used to calculate the number of elements that are in each dimension. However, this time ubound requires the dimension number:

Dim x, y, z

For y = 0 to ubound (apartments)

For x = 0 to ubound (apartments, 2)

For z = 0 to ubound (apartments, 3)

If apartments (y,x,z) <> "" Then

wscript.echo y, x, z, apartments (y,x,z)

End If

The result of this can be seen in figure 2. Of course, there is an important question here. How can the programmer use ubound if they don't know how many dimensions there are?

A Function for Calculating Dimensions

If ubound is used with the wrong number of dimensions (for example if 3 in inputted but there are only 2 dimensions) then an error will occur. However, it is very easy to create a function that will make use of this error to identify the number of dimensions in a multidimensional array. The first step is to stop the function from exiting when the error occurs:

Function dimensions (inarray)

On Error Resume Next

Dim dims: dims = 0

Dim dim_check

The maximum number dimensions allowed by VBScript is 32. It is, therefore, just a matter of counting the dimensions until an error occurs:

Dim i: For i = 1 to 32

dim_check = ubound (inarray, i)

If Err.Number = 0 Then

dims = dims + 1

End If

The number of dimensions that were counted before the error are then returned by the function:

And then the function can be used to calculate the number of dimensions that any array has, for example:

wscript.echo dimensions (name_array)

wscript.echo dimensions (apartments)

The result of this can be seen in figure 3, and the the function will accept variables that are not arrays:

Dim not_an_array

wscript.echo dimensions (not_an_array)

In this way a VBScript programmer can easily find the number of dimensions in a multidimensional array, and it doesn't even matter if there are no dimensions or whether there are 32.

The copyright of the article Find the Dimensions of a Multidimensional Array in Windows Programming is owned by Mark Alexander Bain. Permission to republish Find the Dimensions of a Multidimensional Array in print or online must be granted by the author in writing.