Re: Multiply and Divide operators for geometry types
| От | Thomas Lockhart |
|---|---|
| Тема | Re: Multiply and Divide operators for geometry types |
| Дата | |
| Msg-id | 3CB4DF22.5F0FFE25@fourpalms.org обсуждение исходный текст |
| Ответ на | Multiply and Divide operators for geometry types ("Murphy Pope" <pope_murphy@hotmail.com>) |
| Ответы |
Re: Multiply and Divide operators for geometry types
|
| Список | pgsql-general |
> Can any one explain what the * and / operators are supposed to do?
> For example, what does it mean to multiply a box * a point?
It is equivalent to a translation and a rotation. If you have worked
with complex arithmetic, the analogy is with the real and complex axis,
and the operations which can be done in those two dimensions.
For example, a box consists of four points. Multiplying a box by another
point does the equivalent of a complex math operation on each of those
four points. Multiplying by (1.0,0) has no effect, multiplying by
(0.0,1.0) rotates by 90 degrees, and multiplying by something other than
a unit vector scales also.
Look for stuff on complex math, or perhaps someone has another
suggestion for a reference. Maybe some GIS references would say
something?
- Thomas
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