Re: Shift selection using interactive spec

[Thomas Lord]

Thien-Thi Nguyen wrote:
> () Thomas Lord <address@hidden>
> () Sun, 16 Mar 2008 14:00:03 -0700
>
>    three variable system, most commands DTRT by default, even if
>    they remain ignorant of the three variables.
>
> Do you mean to say "three state"?  To me, three (non-boolean)
> variables implies many many states. 


There are three variables.  Each bound either to nil or a marker.
Under "nominal operating conditions" if any two or three of the
variables are bound to marker, they are bound to the *same*
marker.

So, normally, there are 8 possible states.   And that sounds
hopelessly hairy because 8 *is* a ridiculously large number.
Except that when you look at how they actually work,
it's 8 states in one sense, but in a deeper sense it's a set
of three, orthogonal, binary states:

  Was tentative-mark set when this command was invoked?
     That's maybe-preserved-tentative-mark

  Should tentative-mark be set when this command is done?
    That's preserved-tentative-mark

   Should primitives recognize that there is a tentative mark,
   e.g. by deleting the selected region before any insertion?
      That's tentative-mark.




>  Even if they are all
> boolean, that would mean eight states, ie, a lot of hair.
>
>   

I agree that 8 is a suspiciously large number for something
like this and I encourage people to find a really solid refutation
of my idea.   Please keep trying.   But... 8 in and of itself is
not quite a refutation.

The eight states partition nicely into those three, orthogonal,
binary states.   Those states very simply refer to specific points
in time during the phases of a command cycle.   There's 8, sure,
but really, it's just three, kinda-separate, individually trivial things.

But yes: 8 is a big number and good spotting.   That is
a direction in which to be skeptical, I agree.

-t





> thi
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