Request - add bit shifting

[modsyn]

i recently found out that lua doesn't support shifting bits (ie, <</>>/>>>)
and i found this page with a suggested way of adding the feature:
http://lua-users.org/lists/lua-l/1999-02/msg00024.html

>From: [email protected] (Erik Hougaard)
>This might be a stupid function, but is Lua missing a << >> bitshift function

yes, since it does not make sense for real numbers.

>and if so, how do I make it ?

how about this:

static void math_lshift (void)
{
int v=luaL_check_number(1);
int n=luaL_check_number(2);
lua_pushnumber(v<<n);
}

static void math_rshift (void)
{
int v=luaL_check_number(1);
int n=luaL_check_number(2);
lua_pushnumber(v>>n);
}

lua_register("lshift",math_lshift);
lua_register("rshift",math_rshift);

--lhf

could this possibly be added for future releases?
sorry if i posted this in the wrong place,
modsyn

[fullerlee]

I second this request, I have a need for it in my current project.

Thanks,

Lee

[Shine]

What about x << y == x * math.pow(2, y) and x >> y == math.floor(x / math.pow(2, y)) ?

[fullerlee]

Shine,

I have used mathematics in place of bit shifting, I just thought geniune bit shifting would give some decent performance benefits.

Thanks,

Lee

[Shine]

Do you need the speed? Lua uses always floats as its numbers, so perhaps it would be a better idea to extend the PRX concept of Lua Player and write performance critical parts in your own PRX in C.

[fullerlee]

Time will tell regarding performance. My project involves an AI player and a lot of tree searching, at the moment, performance looks like it might be acceptable, but I've been keeping an eye on the PRX concept.

Keep up the good work!

Thanks,

Lee