From: | Thomas Lockhart <lockhart(at)fourpalms(dot)org> |
---|---|
To: | Murphy Pope <pope_murphy(at)hotmail(dot)com> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Multiply and Divide operators for geometry types |
Date: | 2002-04-11 00:56:02 |
Message-ID: | 3CB4DF22.5F0FFE25@fourpalms.org |
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Lists: | 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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