Re: Operator override and RE: Metatables for primitives performance?

[Chris Marrin <chris@...>]

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().

--
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