WD: ErrMsg Using Mid$(), Left$() or Right$() Function

• Microsoft Word for Windows, versions 6.0, 6.0a, 6.0c
• Microsoft Word for Windows 95, versions 7.0, 7.0a
• Word for the Macintosh, versions 6.0, 6.0.1, 6.0.1a

SYMPTOMS

When you use the Mid$(), Right$() or Left$() functions, you may receive the following error message:

   WordBasic error #24 "Bad parameter"

CAUSE

WARNING: ANY USE BY YOU OF THE CODE PROVIDED IN THIS ARTICLE IS AT YOUR OWN RISK. Microsoft provides this macro code 'as is' without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and/or fitness for a particular purpose.

This problem occurs when the count or length parameter for the statement is negative.

NOTE: In Word 2.0 for Windows, a negative value in the count parameter of the Mid$(), Right$() or Left$() functions is ignored and does not generate an error.

The Mid$() statement returns a portion of a text string starting at a given character position. The syntax for the command is

   Mid$(<source$>, <start> [, <count>])

The following sample macro illustrates the error message described in the "Symptoms" section of this article:

   Sub MAIN
      ReturnText$ = Mid$("hello", 1, -1)
      MsgBox ReturnText$
   End Sub

   Sub MAIN
      Test$ = ""
      Rem Empty string, could be passed as an empty dialog variable for
      Rem example.
      ReturnText$ = Right$(Test$, Len(Test$) - 1)
   End Sub

RESOLUTION

To keep this error from ocurring, first test the length of the string.

For example:

   Sub Main
      ' Empty string, could be passed as an empty dialog
      ' variable, for example.
      Test$ = ""
      ' Test the length of the string to ensure
      ' that subtracting 1 from the length leaves
      ' at least 1 character.
      If Len(Test$) - 1 > 0 then
         ReturnText$ = Mid$(Test$, Len(Test$) - 1)
      End If
   End Sub

REFERENCES

Word Developer's Kit, version 6.0, page 594 Word Developer's Kit, Third Edition, page 660