How to Determine the Current DO Nesting Level

ID: Q104047

2.50 2.50a | 1.02 2.00 2.50 2.50a

WINDOWS    | MS-DOS
 kbprg

The information in this article applies to:

Microsoft Visual FoxPro for Windows, version 3.0
Microsoft FoxPro for Windows, versions 2.5 and 2.5a
Microsoft FoxPro for MS-DOS, versions 1.02, 2.0, 2.5, and 2.5a
Microsoft FoxBASE+ for MS-DOS, version 2.01
Microsoft FoxBASE+ for the Macintosh, version 2.01

SUMMARY

FoxBASE+ and FoxPro allow DO programs to be nested. The maximum number of nesting levels for FoxBASE+ is 24, while FoxPro allows a maximum of 32 levels and Visual FoxPro allows a maximum of 128 levels. Exceeding this limit results in error number 103, "DO nesting too deep."

MORE INFORMATION

DO levels are incremented as follows:

1. When a DO program1 command is issued in the Command window, the DO level

   is set to 1.

2. If program1 includes a DO program2 statement, the DO level is

   incremented to 2. The DO level is incremented each time another DO
   program statement is executed. In this scenario, program1 would be
   referred to as the calling program, and program2 as the called called
   program.

3. If a called program returns to a calling program, either by executing

   all commands in the called program, or by explicitly issuing a RETURN
   command, the DO level is decremented by 1.

The following procedure allows you to determine the current DO level through use of the SYS(16) function. The SYS(16) function returns the name of the currently executing program. It also allows an optional numeric argument that indicates from how many levels back the program name should be fetched.

1. Create a program named DOLVL.PRG with the following commands:

      * Memory variable used:
      * current - name of currently executing program
      * do_ctr - counter which indicates current do level

      current = SYS(16)
      do_ctr = 1
      DO WHILE .T.
         IF SYS(16,do_ctr) <> current
            do_ctr = do_ctr + 1
          ELSE
             * In FoxBASE+ or FoxPro 1.02, remove the word WINDOW
             * in the following command
             WAIT WINDOW "Current DO level is " + STR(do_ctr,1,0)
             EXIT
          ENDIF
      ENDDO

2. Save and execute the program. A message will be displayed as follows:

      Current DO level is 1

3. Create a program named TEST.PRG with the following command and execute

   the program:

      DO dolvl.prg

4. A message will be displayed as follows:

      Current DO level is 2

Additional reference words: VFoxWin 3.00 FoxDos FoxWin 1.02 2.00 2.50 2.50a foxbase+/mac KBCategory: kbprg KBSubcategory: FxenvMemory

Keywords          : kbenv FxenvMemory 
Version           : 2.50 2.50a | 1.02 2.00 2.50 2.50
Platform          : MS-DOS WINDOWS