lua-users home
lua-l archive

[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index] [Thread Index]

On 13 March 2011 13:54, HyperHacker <> wrote:
> I was just thinking, when you write metamethods for an object that
> also has __index and __newindex, you might want to use rawset and
> rawget fairly often to avoid the overhead of invoking those
> metamethods (since you probably don't need/want them for internal
> methods such as these). However, each property you want to read/write
> using rawset and rawget is another function call, which also has some
> overhead.
> You could avoid this by modifying rawset and rawget to accept multiple
> parameters and return multiple values, i.e.:
> local a, b, c = rawget(self, 'a', 'b', 'c')
> rawset(self, 1, a, 2, b, 3, c) --or:
> rawset(self, {a, b, c})
> (As an example, I wrote a Vector3 class which provides __index and
> __newindex to access the elements as v.x, v.y, v.z and v.r, v.g, v.b
> for convenience, but actually stores them as v[1], v[2], v[3]. For
> __add, __sub etc it's probably a lot more efficient not to go through
> __index 6 times (3 per vector). Though, while writing I realized
> __index isn't invoked for existing keys anyway, but that was where the
> idea came from... Still, any code doing multiple rawget/rawset calls
> on the same object could benefit from this.)
> --
> Sent from my toaster.

A different modification to rawset I've always wanted is to have it
return the value.
Its far too common in my code to see:
__index = function(t,k)
    local v = foo(k)
    return v

This could all be swapped out for tailcall:
return rawset(t,k,foo(k))

A problem with your proposal would be that raw* which is generally a
very simple (and fast) base level function; now has to iterate over
it's arguments.