sidereal.py: Internal maintenance specification

This is pretty similar to Section 4.5, “checkArgs(): Process command-line arguments”, except that the first item is an azimuth, sign, and altitude.

# - - -   c h e c k A r g s

def checkArgs():
    """Process all command line arguments.

      [ if sys.argv[1:] is a valid set of command line arguments ->
          return (altAz, latLon, dt) where altAz is a set of
          horizon coordinates as a sidereal.AltAz instance,
          latLon is position as a sidereal.LatLon instance, and
          dt is a datetime.datetime instance
        else ->
          sys.stderr  +:=  error message
          stop execution ]
    """

    #-- 1 --
    # [ if sys.argv[1:] has exactly four elements ->
    #     rawAltAz, rawLat, rawLon, rawDT  :=  those elements
    #   else ->
    #     sys.stderr  +:=  error message
    #     stop execution ]
    argList  =  sys.argv[1:]
    if  len(argList) != 4:
        usage ("Incorrect command line argument count." )
    else:
        rawAltAz, rawLat, rawLon, rawDT  =  argList

For the checking of the first argument, see Section 5.7, “checkAltAz(): Validate horizon coordinates”. The rest are as in Section 4.5, “checkArgs(): Process command-line arguments”.

    #-- 2 --
    # [ if rawAltAz is a valid set of horizon coordinates ->
    #     altAz  :=  those coordinates as a sidereal.AltAz instance
    altAz  =  checkAltAz ( rawAltAz )

    #-- 3 --
    # [ if rawLat is a valid latitude ->
    #     lat  :=  that latitude in radians
    #   else ->
    #     sys.stderr  +:=  error message
    #     stop execution ]
    try:
        lat  =  sidereal.parseLat ( rawLat )
    except SyntaxError, detail:
        usage ( "Invalid latitude: %s" % detail )

    #-- 4 --
    # [ if rawLon is a valid longitude ->
    #     lon  :=  that longitude in radians
    #   else ->
    #     sys.stderr  +:=  error message
    #     stop execution ]
    try:
        lon  =  sidereal.parseLon ( rawLon )
    except SyntaxError, detail:
        usage ( "Invalid longitude: %s" % detail )

    #-- 5 --
    # [ if rawDT is a valid date-time string ->
    #     dt  :=  that date-time as a datetime.datetime instance
    #   else ->
    #     sys.stderr  +:=  error message
    #     stop execution ]
    try:
        dt  =  sidereal.parseDatetime ( rawDT )
    except SyntaxError, detail:
        usage ( "Invalid timestamp: %s" % detail )

    #-- 6 --
    latLon  =  sidereal.LatLon ( lat, lon )
    return  (altAz, latLon, dt)