Re: Multiply and Divide operators for geometry types

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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> 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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