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

ID: Q108709

The information in this article applies to:

Standard and Professional Editions of Microsoft Visual Basic for Windows, versions 2.0 and 3.0

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

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

From the File menu, choose New Module.

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

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.

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

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

From the File menu, choose New Module.

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

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

Keywords : kbcode PrgOther
Version : 2.00 3.00
Platform : WINDOWS
Issue type :