20-Feb-2009

The following are suggested guidelines for IDL procedures to be submitted
to the IDL Astronomy Library

(1) Each procedure should include documentation in a format similar to that
        described in the file $IDL_DIR/examples/template.pro (Unix) and used
    in the standard IDL Users Library.    The documentation must be bracketed
    by ;+ and ;-  symbols so that it may be extracted by the help software.  
    The NAME: and  CALLING SEQUENCE: fields must be used and the purpose and
    types of all  parameters and keywords should be explained.   Following the
    NAME: field,  there should be a PURPOSE: field giving a one-line
    description.   Any further description can then be supplied under a
    (optional) EXPLANATION: field.

(2) The use of function calls is discouraged.    If a function call is
    used it should have name that is not likely to be used as an array in 
    another unrelated program, e.g. DAO_VALUE() is probably O.K, but VALUE() is 
    not. 

(3) The procedures should be as platform independent as possible.  This 
    generally means having IF statements when spawning to the operating 
     system, e.g.

   if !version.os_family EQ 'MacOS' then nozero1 = 0

 
(4) The procedure should display the calling sequence if insufficient
   parameters are supplied.   Keyword parameters should always be optional.

(5) The use of non-standard system variables is discouraged.

  For historical reasons, the IDL Users Library currently uses three extra
  system variables that are  added with the DEFSYSV procedure.   They are

  !PRIV - Used in a couple of the database programs.   Needs to be set when
          modifying a database.
  !TEXTOUT - Used in the program TEXTOPEN which is called by the database and
        several other programs.   Programs which use this non-standard system
        variable also allow a keyword TEXTOUT to be used instead of the 
       system variable
  !TEXTUNIT - Logical output unit number used by TEXTOPEN

   These three additional system variables can be added to one's session 
      using the procedure ASTROLIB.