Re: Multiply and Divide operators for geometry types
От | Thomas Lockhart |
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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
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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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