How do I use the bitwise operator XOR in Lua?

Question

How can I implement bitwise operators in Lua language?
Specifically, I need a XOR operator/method.

Answer 1

Since you're referencing the floor function 3 times, using an excessive number of loops for most operations (numbers less than 2^31 don't need all 31 loops), are using the ^ operator, and aren't capitalizing on the fact that a and b might be wildly different numbers with different magnitudes, you're losing a lot of efficiency. The function also isn't localized, and you're doing two more division operations than you need to. I wrote this to be reasonably fast.

In general, you're going to see improvements of about 3 to 20 times.

local function BitXOR(a,b)--Bitwise xor
    local p,c=1,0
    while a>0 and b>0 do
        local ra,rb=a%2,b%2
        if ra~=rb then c=c+p end
        a,b,p=(a-ra)/2,(b-rb)/2,p*2
    end
    if a0 do
        local ra=a%2
        if ra>0 then c=c+p end
        a,p=(a-ra)/2,p*2
    end
    return c
end

If you need more than this, say AND, OR, and NOT, then I've got you covered there, too.

local function BitOR(a,b)--Bitwise or
    local p,c=1,0
    while a+b>0 do
        local ra,rb=a%2,b%2
        if ra+rb>0 then c=c+p end
        a,b,p=(a-ra)/2,(b-rb)/2,p*2
    end
    return c
end

local function BitNOT(n)
    local p,c=1,0
    while n>0 do
        local r=n%2
        if r<1 then c=c+p end
        n,p=(n-r)/2,p*2
    end
    return c
end

local function BitAND(a,b)--Bitwise and
    local p,c=1,0
    while a>0 and b>0 do
        local ra,rb=a%2,b%2
        if ra+rb>1 then c=c+p end
        a,b,p=(a-ra)/2,(b-rb)/2,p*2
    end
    return c
end

Don't worry, you won't need to change anything.