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Conference azur::mcc

Title:	DECmcc user notes file. Does not replace IPMT.
Notice:	Use IPMT for problems. Newsletter location in note 6187
Moderator:	TAEC::BEROUD

Created:	Mon Aug 21 1989
Last Modified:	Wed Jun 04 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	6497
Total number of notes:	27359

1548.0. "Specify NULL Set to BITSET attribute?" by SYSMGT::DUTKO (Nestor, VMS Engineering) Wed Sep 25 1991 14:10

I have a data type defined as:

    TYPE VMS_UIC_AccessBits = 9001
        ( R = 0,
          W = 1,
          E = 2,
          D = 3
        );

    TYPE VMS_UIC_Access = 9020 BITSET OF VMS_UIC_AccessBits;

    TYPE VMS_UIC_Protection = 9003 RECORD
        System  = 1 : VMS_UIC_Access;
        Owner   = 2 : VMS_UIC_Access;
        Group   = 3 : VMS_UIC_Access;
        World   = 4 : VMS_UIC_Access;
        END ;

One of the attributes of the entity I'm developing (lets call it DISK), uses 
the data type VMS_UIC_Protection. 

What I'd like to do is issue the command:

SET NODE 0 DISK DKB300 Protection {System={R,W}, Owner={R,W,E,D}, Group={R,E},
	World{} }

(Yes, in effect I want to have WORLD be the NULL set.) When I issue the command
to the V1.1 FCL, I get the error: 

	%MCC-E-ENUMERATION_ERR, no such Enumeration value

Is there any way that I can get what I want?

T.R	Title	User	Personal Name	Date	Lines
1548.1	empty record value.	TOOK::CALLANDER	MCC = My Constant Companion	`Wed Sep 25 1991 19:46`	9
	Off the top of my head I can't think of a way. What we currently do in similar situations is to have a value called NULL or None or something like that that can be entered. Yes I know that isn't great. Let me think about it some more. I am simply not ccertain how from a parse stand point I can solve it. !! unless the v1.2 null set support will allow a null bitset!! let me get back to you (send mail if you don't hear from me in the near future). jill
1548.2	Surely its a bug	MARVIN::COBB	Graham R. Cobb (Wide Area Comms.), REO2-G/H9, 830-3917	`Mon Sep 30 1991 09:59`	10
	This is just a straight bug, right? BITSETs are no different from any other sets as far as the user is concerned (the only difference is in the way they are encoded on the wire). A null set is a null set is a null set. The problem here isn't a missing record field but a field with a perfectly legal set value (that happens to be the empty set). It will be fixed, won't it? BITSETs are used in Phase V management and need to work! Graham
1548.3		MAVIC::D_MOORE		`Tue Oct 08 1991 16:01`	18
	Yes, this is simply a bug. Jill, it is not a matter of sending a "null" value, as in an mcc_a_pointer of null. Taking an example like Nestor's, if you have: Days_of_week : (Sunday, Monday, ..., Saturday) Days : BITSET OF Days_of_week A null value for Days is simply a bitset with all bits set to zero and the user input is "()". "A null set is a null set is a null set", as Graham said. Wherever this is broken in MCC, it should not be a big deal to fix it. The various pieces were put together with this in mind. It is no harder to parse a null BITSET than it is to parse a null SET OF -- they can both be represented by "()". However, the internal representation of those values are different because the data types are different. - Dave
1548.4	null bitsets in v1.2	TOOK::CALLANDER	MCC = My Constant Companion	`Thu Oct 17 1991 18:42`	5
	I made the changes, Dave is taking care of the SRM (BNF doesn't allow for null sets to be entered for the bitset). But, I had better double check that I checked the file back in!! Thanks for pointing it out.
1548.5	Care to test it?	MARVIN::COBB	Graham R. Cobb (Wide Area Comms.), REO2-G/H9, 830-3917	`Tue Oct 22 1991 17:01`	7
	Thanks for do ing that. It would be useful to test out the BITSET support. Care to try some experiments with (DNA5) MOP CIRCUIT FUNCTIONs? We can probably help (e.g. suggest some things to try and provide a node to try them to). Graham
1548.6	request for exampls	TOOK::CALLANDER	MCC = My Constant Companion	`Wed Nov 06 1991 16:37`	4
	sure, give me some examples to try. jill