zz: Coplanar marking explained

[Ted Nelson <ted@xxxxxxxxxx>]

You ask

>(2) how "selection groups" work and
>what they are for?

I presume you mean coplanar marking, never yet
 implemented.  

In both the Perl and Gzz versions, marking is an on-off
 toggled attribute of a cell.  I have a much broader plan.

A mark (or selection group) is a set of cells selected.
 The mark is persistent, and any number of groups may
 be selected at once.  A cell may be marked by any
 number of marks.

It is also one of the overall designs that *every operation
 that works on one cell should also work on a marked group
 of cells*.  This will take some time to work out for each
 operation.

The way it works is this: Each mark is a group of cells
 connected together in an area that is in principle away from
 the marked cells.  For every marked cell there is a marking
 cell.

(I'm not looking up previous explanations; hope this is
 consistent.)

The marking-cell is connected to the marked cell in d.mark.

All the cells in a particular mark are connected, could be
 on d.1.  That means--
 - if you know one marking-cell of a particular mark, you
 can find the others easily
 - if you know any of the marked cells and any of the marking
 cells, you can find the other cells of the same mark
 
The headcell of a particular mark (on d.1) is probably the
 best one for referring to the entire mark.  But we may
 want to have a reference token to take elsewhere to identify
 the mark.  We would light up some particular mark and
 do on operation on the selected cells by-- let's say--
 - selecting one of these headcells with the left cursor;
 - this would light up the selection;
 - performing the operation with the right cursor,
which then takes place with the whole bunch.  (For instance,
 Hop would hop the whole bunch.
 
The headcells of the mark probably should not participate
 in the mark, but simply be connected along d.mark to some
 conspicuous cell, such as Home.

I currently call this "coplanar marking" because the cells
 of any particular mark are all in the same plane.  I thought
 I had a use for some second dimension of marking, but
 at the moment can't remember it.

There's more to work out about this, but it's the general idea.

Best, Ted


_________________________________________
Theodor Holm Nelson              
Project Professor, Keio University SFC Campus, Fujisawa, Japan
Visiting Professor, University of Southampton, England
 ?  e-mail: ted@xxxxxxxxxx   ?  world-wide fax 1/415/332-0136
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 ? Coordinates in USA      Tel. 415/ 331-4422
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