12-Aug-1995

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/general/template.pro (Unix)
    or IDL_DIR:[EXAMPLES.GENERAL]TEMPLATE.PRO (VMS) 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.

(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 EQ "vms" then spawn,'TYPE FILE.DAT' else spawn,'more file.dat'

    For Windows-IDL compatibility the procedure names should be unique in the 
    first 8 characters.    The Library currently violates this rule for the 
    following pairs of procedures

    dfitsread,dfitsread_large         minf_parabol_d, minf_parabolic
    tab_null, tab_nullrow             copy_struct,copy_struct_inx

(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.

  The IDL Users Library currently uses four extra system variables that are 
  added with the DEFSYSV procedure.   They are

  !DEBUG - Used to determine if additional debugging information should be 
           set
  !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 4 additional system variables can be added to one's session using the
   procedure ASTROLIB.