zz: Headcells and corner lists (wuz Re: [zzdev] :gzz: Corner lists (wuz Re: [zzdev] Re: [zzdev] Direct ion and name of d.cursor

[Ted Nelson <ted@xxxxxxxxxx>]

Tuukka asks:

>Do I get this right: headcell is the negend cell, unless the negend
>cell is blank. When the negend cell is blank, it's a corner list and
>the headcell is something else? And what then? If we are to show the
>headcell somehow differently, we should have an exact way to define it.

? The headcell is either the negend, or, in the case of
 a looping rank, some particular cell which has been designated.

Right now there is no way to designate a headcell on a looping rank,
 but when there is such a thing, we'll also need a toggle to show it,
 as with every other trait.

? "Corner list" is a term that combines a structure and an expected
 function.  You can have that same structure for some other purpose
 and not necessarily consider it a corner list.

The idea is that you reach the list by a cell connected on another
 dimension, and it's a useful list of some kind, in principle
 user-readable.

The top cell need not be empty, but right now that's the only way
 you can conveniently rearrange the significant items on the list--
 the top one is locked in place by its sideways connection.  But
 after we implement "chug", it'll be easy to rearrange the whole
 corner list, including the top element.

Best, Ted


At 03:48 PM 7/11/00 +0300, you wrote:
>On 11 Jul, Ted Nelson wrote:
>>>Actually, we often write this like
>>>
>>> |heading|-|  +      |
>>>           |chapter 1|
>>>           |chapter 2|
>>>           |chapter 3|
>>>           ...
>>>
>>>i.e. inserting a dummy cell *exactly* because of this.  This is called
>>>a corner list.  At this point, all chapters are headcells.
>
>This practise is good to know.
>
>> This is not necessarily the only form of a corner list--
>>  it's a corner list with an empty cell at the top, making it easier
>>  to rearrange.
>> 
>> As soon as we have the Chug operation, that empty cell will
>>  be less necessary.
>
>Without the empty cell, how do you actually know it's a corner list?
>
>Do I get this right: headcell is the negend cell, unless the negend
>cell is blank. When the negend cell is blank, it's a corner list and
>the headcell is something else? And what then? If we are to show the
>headcell somehow differently, we should have an exact way to define it.
>
>----------------------------------------
>E-Mail: Tuukka.Hastrup@xxxxxx
>WWW:    http://www.iki.fi/Tuukka.Hastrup
>ICQ:	#11321669
>
>
>
_________________________________________
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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