--[[
The function does curve conversion f(v) = outputValue
Example of a curve, having multiple ranges of kx + b, set in a register of a String type with Json 
[{"k":4.167,"b":0,"range":[0,3]},{"k":0,"b":12.5,"range":[3,27]},{"k":-4.167,"b":125,"range":[27,30]}]
--]]
function getCurveValue (curveReg, v)
 
    local start, end_ = 1, 2                           -- start & end indexes of the subranges 
    local tab = cjson.decode(R(curveReg))
    
    -- edge cases go first 
    if  (v < tab[start].range[start]) then 
        return tab[start].range[start] * tab[start].k + tab[start].b, true
    elseif (v > tab[#tab].range[end_]) then 
        return tab[#tab].range[end_] * tab[#tab].k + tab[#tab].b, true 
    end
 
    for _, sub_ in ipairs(tab) do 
        if ( (sub_.range[start] <= v) and (v < sub_.range[end_]) ) then 
            return (v * sub_.k + sub_.b), false                             -- normal sequence 
        end
    end
end