EXIST(SEXP) (BOOLEAN)

 Function
  Determine whether or not a file exists.

 Syntax
  EXIST(file)

   file = A string expression with the drive, path and file name to check.

 Return Type & Value
  BOOLEAN
  Returns TRUE if the file exists on the specified drive and path,
  FALSE otherwise.

 Remarks
  It is often necessary to check for the existence of a file.  For example,
  you wouldn't want to display or otherwise process a file that doesn't
  exist.  This function will report whether or not a specified file exists
  on a particular drive and path.  The drive will default to the current
  drive and the path will default to the current directory if not
  specified.

 Examples
  STRING file
  LET file = "NEWS."+STRING(CURNODE())
  IF (EXIST(file)) DISPFILE file,0