Preprocessor Directives Incorrect in "Language Tips" Help

ID: Q118617

The information in this article applies to:

Microsoft FoxPro for Windows, versions 2.5, 2.5a, 2.5b, 2.6
Microsoft FoxPro for MS-DOS, versions 2.5, 2.5a, 2.5b, 2.6
Microsoft FoxPro for Macintosh, versions 2.5b, 2.5c

In the "Language Tips" section of the online Help file, under the "Tips and Tricks" topic, the second paragraph under the "Preprocessor Directives" topic incorrectly states the following:

   This code would not work because _DOS would be changed to .T. and
   _WINDOWS would be changed to .F. so that the code could never work
   properly again. Instead use the following:

      #IF "Win" $ VERS()
      #DEFINE windows_code .T.
      #ELIF "Mac" $ VERS()
      #DEFINE mac_code .T.
      #ELIF "Unix" $ VERS()
      #DEFINE unix_code .T.
      #ELSE
      #DEFINE dos_code .T.
      #ENDIF
      #IF windows_code
      ? "Compiled under WINDOWS"
      #ELIF dos_code
      ? "Compiled under DOS"
      #ENDIF

This resolution code is incorrect because FoxPro does not allow nested preprocessor directives. When you compile the code above, it will create an .ERR file with the same name as the source file if the .ERR File option is selected in the Compile dialog box. The *.ERR file will log the following errors:

   #elif "Mac" $ VERS()
   Error in line 3: Mismatched #if/#elif/#else/#endif.
   #elif "Unix" $ VERS()
   Error in line 5: Mismatched #if/#elif/#else/#endif.
   #else
   Error in line 7: Mismatched #if/#elif/#else/#endif.
   #endif
   Error in line 9: Mismatched #if/#elif/#else/#endif.

The correct resolution code is:

   #DEFINE win_code "Win" $ VERS()
   #DEFINE mac_code "Mac" $ VERS()
   #DEFINE unix_code "Unix" $ VERS()
   #DEFINE dos_code NOT("Win" $ VERS() OR "Mac" $ VERS() ;
      OR "Unix" $ VERS()))
   #IF win_code
   ? "Compiled under WINDOWS"
   #ELIF dos_code
   ? "Compiled under DOS"
   #ENDIF

Additional reference words: FoxMac FoxDos FoxWin 2.50 2.50a 2.50b 2.50b 2.60 docerr KBCategory: kbprg kbdocerr KBSubcategory: FxprgGeneral

Last Reviewed: June 27, 1995