Re: [SQL] line datatype

Lamar Owen wrote:
> On Tuesday 16 July 2002 11:29 am, Thomas Lockhart wrote:
> > > > We do need a solution for exact dump/reload of floating-point data,
> > > > but I don't see why the lack of it should be reason to disable access
> > > > to the LINE type.
>
> > > I don't understand why dumping the two point values isn't sufficient.
>
> > Which two point values? LINE is handled as an equation, not as points,
> > unlike the LSEG type which has two points.
>
> > One possibility is to have the external representation *be* the same as
> > LSEG, then convert internally. Then we need to decide how to scale those
> > points; maybe always using a unit vector is the right thing to do...
>
> Lines are entered now by specifying two points, anywhere on the line, right?
> The internal representation is then slope-intercept? Why not allow either
> the 'two-point' entry, or direct entry as slope-intercept? How do we
> represent lines now in output? Do we pick two arbitrary points on the line?
> If so, I can see Thomas' point here, where the original data entry might have
> specified two relatively distant points -- but then there's a precision error
> anyway converting to slope-intercept, if indeed that is the internal
> representation. So why not dump in slope-intercept form, if that is the
> internal representation?

Yow, I can see the pain of having slope/intercept and trying to output
two points. What if we store line internally as two points, and convert
to slope/intercept when needed. That way, it would dump out just as it
was entered.

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