Q108709: Expected Expression Error: Dynamic Array Not OK in User-Type

Article: Q108709
Product(s): Microsoft Visual Basic for Windows
Version(s): 2.0,3.0
Operating System(s): 
Keyword(s): kbcode
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Standard Edition for Windows, versions 2.0, 3.0 
- Microsoft Visual Basic Professional Edition for Windows, versions 2.0, 3.0 
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SYMPTOMS
========

An "Expected: expression" error occurs within a Type statement in Visual Basic
when you follow an array name with empty parentheses ().

You can use the Type ... End Type statement block to define your own data type
using Basic's predefined data types as components. You can dimension variables
or arrays using that user-defined type.

CAUSE
=====

Visual Basic interprets the empty parentheses () that follow a variable name in
the Type statement as a declaration of a dynamic array. Visual Basic does not
allow dynamic arrays to be declared within a user-defined Type statement block.

RESOLUTION
==========

Within the Type ... End Type statement block, parentheses that follow a variable
name must contain a number to indicate the number of elements in a static array.
Visual Basic allows Type statements to contain static arrays but not dynamic
arrays.

NOTE: Once you correctly define a user-defined type, you can dimension a dynamic
array of that type. See further below for an example.

STATUS
======

This behavior is by design.

MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

1. Start a new project in Visual Basic. Form1 is created by default.

2. From the File menu, choose New Module.

3. Add the following code to the new module, MODULE1.BAS:

     Type newinfo
        tarray() as string  'Gives "Expected: Expression" error on ()
        numstores As Long
     End Type

4. Edit the line containing tarray(). Then select any other line. The automatic
  syntax checker in Visual Basic correctly highlights the () and gives the
  following error:

  Expected: Expression

  Running the program by pressing the F5 key also correctly reports this syntax
  error.

5. To correct this programming error, add a number of array elements in the
  empty parentheses. For example, change tarray() to tarray(10). This changes
  the array from dynamic to static.

Visual Basic interprets the empty parentheses in tarray() in the Type statement
as a declaration of a dynamic array. Visual Basic does not allow dynamic arrays
to be declared within a user-defined Type ... End Type statement block. The
parentheses () must contain a number to indicate the number of elements in a
static array.

How to Make a Dynamic Array of User-Defined Type
------------------------------------------------

1. Start a new project in Visual Basic. Form1 is created by default.

2. From the File menu, choose New Module.

3. Add the following code to the new module, MODULE1.BAS:

     Type newinfo
        tarray(20) As String  'Static array declared in user-defined type
        numstores As Long
     End Type

4. Double-click Form1 to display the form's code window. Add the following to
  the form load event:

     Sub Form_Load ()
        ' Use ReDim to declare or redimension a dynamic array:
        ReDim arrayx(20) As newinfo  'Make dynamic array of user-defined type
        arrayx(18).tarray(12) = "Ruby slippers"       ' Assign value.
        arrayx(18).numstores = 999                    ' Assign value.
        form1.Show  ' In load event, must Show form before Print can work.
        Print arrayx(18).tarray(12)   ' Print value.
        Print arrayx(18).numstores    ' Print value.
     End Sub

NOTE: You cannot change the number of elements in static arrays at run time, but
you can use the ReDim statement to change the number of elements in dynamic
arrays.

REFERENCES
==========

  Visual Basic version 3.0 for Windows, "Programmer's Guide," Chapter 7,
  "User-Defined Types (Structures)", pages 176-178. A user-defined type can
  contain an ordinary (fixed-size) array, but not a dynamic array.

Additional query words: 2.00 3.00

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Keywords          : kbcode 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB300Search kbVB300 kbVB200
Version           : :2.0,3.0

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