Settings = {
    Name = "*GAT (Bill Williams Alligator)",
    Round = "off",
    VType = "Median", --Median price
    -- parameters
    metod = "RMA",
    kScaleFakr = 0.0001,
    -- script is working up until I add third moving avrg line
    schift_A =  3, --short shift forward
    period_A =  5, --short period
    schift_B =  5, --long shift forward
    period_B =  8, --long period
    --
    line = {
        {
            Name = "GAT_0",
            Type = TYPE_LINE,
            Width = 1,
            Color = RGB(0,255,0)
        },{
            Name = "GAT_1",
            Type = TYPE_LINE,
            Width = 1,
            Color = RGB(255,159,64)
        }
    }
}

function Init()
    func = r_MAIN()
    return #Settings.line
end

function OnCalculate(Index)
    return func(Index, Settings)
end

function r_MAIN()
    local vA_MA=r_RMA()
    local vB_MA=r_RMA()
    return function(I, Fsettings, ds)
        local Fsettings=(Fsettings or {})
        local R  = (Fsettings.Round or "off")
        local VT = (Fsettings.VType or "Median")
        local oA,oB --output values
        oA = nil; oB = nil;
        --
        local M  = (Fsettings.metod or "RMA")
        local k_sc = (Fsettings.kScaleFakr or 0.0001)
        --
        local s_A = (Fsettings.schift_A or 3)
        local p_A = (Fsettings.period_A or 5)
        local s_B = (Fsettings.schift_B or 5)
        local p_B = (Fsettings.period_B or 8)
--      local s_C = (Fsettings.schift_C or 8)
--      local p_C = (Fsettings.period_C or 13)
        --
        vA = vA_MA(I, VT, ds, p_A)
        vB = vB_MA(I, VT, ds, p_B)
        --
        if ( vA ~= nil ) then oA=vA end
        if ( vB ~= nil ) then oB=vB end
        --
        return oA,oB
    end
end

-----------------
function r_RMA()
    local RMA={}
    return function(I ,VT, ds, Period)
        local P = ((Period) or 5)
        local value = nil
        local grace = 15 --grace period to filter out bad initial period
        --
        -- we perform logarithm over price often
        -- so we must use positive value, this time its 1.0
        if (I==1) then --protection from candle(1) not-existing
            RMA[I]=1.0; return RMA[I]; 
        end
        --
        if (CandleExist(I)) then
            value = (H(I)+L(I))*0.5 --median
            if (value~=nil) then
                if (I < grace) then
                    -- early values are getting averaged
                    -- so they get faster to real indicator
                    RMA[I] = 0.5*( value + RMA[I-1] )
                else
                    RMA[I] = ( (P-1) * RMA[I-1] + value )/P
                end
            else -- candle exist, but value does not
                RMA[I]=RMA[I-1]
            end
            --
        else -- candle does not exist
            RMA[I]=RMA[I-1]
        end
        --
        return RMA[I]
    end
end