velocityStacks.lua

local ret = {}

ret.new = function (self, stackLength)
    local thing = {}
    thing.speed = 10
    thing.stack = {}
    for i=1,stackLength do
        thing.stack[i] = 0
    end

    thing.update = function(self, dt)
        --dt is in seconds passed
        --at 60 fps it would be 0.01667

        --equation for framerate independence is ((1/(framerate/-0.6))+1)
        --dt is 1/framerate, framerate is 1/dt
        --final equation: (1/((1/dt)/-0.6))+1 = 1-(0.6*dt)

        local t = 1-(self.speed*dt)
        if t < 0 then t = 0 end -- <--for SUPER low framerates
        for i=2,#(self.stack) do
            --self.stack[i] = (self.stack[i] + self.stack[i-1]) * 0.5
            self.stack[i] = ((1-t) * self.stack[i-1]) + (t * self.stack[i])
        end

        --[[
        for a 2 item stack
        1: [1]
        2: ([2] + [1]) / 2

        for a 3 item stack
        1: [1]
        2: ([2]+[1]) / 2
        3: ([3]+[2]) / 2

        well now it's lerp instead of average
        if you wanted average at 60fps then change the 0.6 to 30
        the right value being 90% would be 6
        the right value being 10% would be 0.015
        1% = 59.4, 0.1% = 59.94, 0% = 60
        so if a frame lasts 0 seconds exactly, the values don't change
        ]]
    end

    --set all values in the stack to a given value
    thing.init =  function(self, value)
        for i=1,#(self.stack) do
            self.stack[i] = value
        end
    end

    --define metatable if it isn't defined already
    if not self.mathObjectMT then
        --make metatable for math interactions
        self.mathObjectMT = {} --is this something you can do? idk
        self.mathObjectMT.__utilGetNumber = function (value) --return number from value of unknown type
            if type(value) == "table" then
                if value.stack then --if it has a stack
                    return value.stack[#(value.stack)]
                elseif value.currentValue then --if it has a currentValue
                    return value.currentValue

                else --if there were to be another special number type to check for, that goes here
                    return nil
                end
            elseif type(value) == number then
                return value
            else --some other random type like a string
                return nil
            end
        end
        --define math functions
        self.mathObjectMT.__add = function(a,b) -- a+b
            local getNum;
            if type(a) == "table" and a.stack then
                getNum = getmetatable(a).__utilGetNumber
            else
                getNum = getmetatable(b).__utilGetNumber
            end
            return getNum(a) + getNum(b)
        end
        self.mathObjectMT.__sub = function(a,b) -- a-b
            local getNum;
            if type(a) == "table" and a.stack then
                getNum = getmetatable(a).__utilGetNumber
            else
                getNum = getmetatable(b).__utilGetNumber
            end
            return getNum(a) - getNum(b)
        end
        self.mathObjectMT.__mul = function(a,b) -- a*b
            local getNum;
            if type(a) == "table" and a.stack then
                getNum = getmetatable(a).__utilGetNumber
            else
                getNum = getmetatable(b).__utilGetNumber
            end
            return getNum(a) * getNum(b)
        end
        self.mathObjectMT.__div = function(a,b) -- a/b
            local getNum;
            if type(a) == "table" and a.stack then
                getNum = getmetatable(a).__utilGetNumber
            else
                getNum = getmetatable(b).__utilGetNumber
            end
            return getNum(a) / getNum(b)
        end
        self.mathObjectMT.__pow = function(a,b) -- a^b
            local getNum;
            if type(a) == "table" and a.stack then
                getNum = getmetatable(a).__utilGetNumber
            else
                getNum = getmetatable(b).__utilGetNumber
            end
            return getNum(a) ^ getNum(b)
        end
        self.mathObjectMT.__unm = function(a) -- -a
            return -(getmetatable(a).__utilGetNumber(a))
        end
    end
    setmetatable(thing, self.mathObjectMT)

    return thing
end

return ret