Re: The real problem with vectors and Lua (Atomic Tuples)

[John Belmonte <jvb@...>]

Dylan wrote:
> Something like   (this is totally off the top of my head.. don't rip me to
> shreds)
>
> position = << 10, 20, 30 >>    -- create a "tuple"
> position.another_value = 10    -- ERROR.. position isn't a table and is a
> "const" in effect
>
> position<<x>> = 30        -- creates a new "const" vector with x as 30 and
> the rest from position
> position<<x,y>> = 50, 70  -- writes to x, y, and takes z from position,
> creating a new vector

I haven't been following this thread too carefully, but userdata is what you 
want.  It seems like you are on that path anyway.

Don't be afraid to let these vectors exist as either your native aligned format 
or a Lua array depending on what is convenient.  You just need to be able to 
translate between the two.  So I'd rewrite what you have above as:

position = Vector { 10, 20, 30 }        -- Vector_XYZ is assumed
position.another_value = 10             -- ERROR
position:Set(Vector_X { 30 })           -- you might also support Vector_X(30)
                                        --     for efficiency
position:Set(Vector_XY { 50, 70 })

-- other stuff
lua_array = position.ToArray()
lua_array[0] = 25.5                     -- assuming you break Lua convention and
                                        --     start your array at 0 :-(
position_b = Vector(lua_array)
position_c = position * position_b      -- your efficient native operation
point = Vector_XY(position_c)           -- extract XY as vector
z = Vector_Z(position_c):ToNumber()     -- extract Z as Lua number
z = position_c:ToArray()[2]             -- same thing
z = position_c:GetScalarZ()             -- same thing
point_b = Vector(point)			-- copy


If you haven't seen it, "Vector { 1, 2, 3 }" is table constructor syntax, 
equivalent to Vector({1, 2, 3}).

This isn't too far off from your C++ vector template stuff...

-John



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