Re: Operator override and RE: Metatables for primitives performance?
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- Subject: Re: Operator override and RE: Metatables for primitives performance?
- From: Chris Marrin <chris@...>
- Date: 2006年3月25日 20:44:01 -0800
Jerome Vuarand wrote:
Hi list,
I was porting an old C++/Java school project to Lua, and it contains a
vector3 class representing a position/vector in 3d space. Since I'm using
Lua 5.1 since the day it's out, I thought it would have been nice to use
the # operator to get the length of the vector. My vector is a table with
x, y and z fields, and I don't care about the length of the table itself.
My problem is that I then figured out that the # operator is not
overridable
for tables, since it already exists. I thought it was a bug of some
kind, but
the Lua source seems to be explicit about that:
...
I have implemented a similar object. But I implemented it as a userdata
with space for 3 floats. Then I override the __index and __newindex
metamethods to access the components. The nice thing about this is that
I can use a.y and a[1] styles of component access and get to the same
components. I've also overridden arithmetic operations so I can add and
subtract vectors. This method also allows the use of the '#' operator
for length().
--
chris marrin ,"",ドル "As a general rule,don't solve puzzles
chris@marrin.com b` $ that open portals to Hell" ,,.
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```"```'" `"` `""` ""` ,P`