gistfile1.lua

local cardinals = {
    up = new(0, 1),
    down = new(0, -1),
    left = new(-1, 0),
    right = new(1, 0)
}

function vector:closestCardinal(v)
    local maxDistance = 0
    local longestVec

    for name, cardinalVector in pairs(vector.cardinals) do
        local projected = v:projectOn(cardinalVector)
        local projectedLength = projected:len2()
        if projectedLength > maxDistance then
            longestVec = projected
            maxDistance = projectedLength
        end
    end

    assert(longestVec)
    return longestVec:normalize_inplace()
end