cumulative probability, Lua

cumulative probability

function dump (tbl, indent)
  if not indent then indent = 0 end
  local toprint = string.rep(" ", indent) .. "{\r\n"
  indent = indent + 2 
  for k, v in pairs(tbl) do
    toprint = toprint .. string.rep(" ", indent)
    if (type(k) == "number") then
      toprint = toprint .. "[" .. k .. "] = "
    elseif (type(k) == "string") then
      toprint = toprint  .. k ..  "= "   
    end
    if (type(v) == "number") then
      toprint = toprint .. v .. ",\r\n"
    elseif (type(v) == "string") then
      toprint = toprint .. "\"" .. v .. "\",\r\n"
    elseif (type(v) == "table") then
      toprint = toprint .. dump(v, indent + 2) .. ",\r\n"
    else
      toprint = toprint .. "\"" .. tostring(v) .. "\",\r\n"
    end
  end
  toprint = toprint .. string.rep(" ", indent-2) .. "}"
  return toprint
end

local items = { [1] = {id = "bandage", w = 2}, [2] = {id = "bow", w = 4}, [3] = {id = "gold", w = 1}, [4] = {id = "apple", w = 5} }
table.sort( items, function(a, b) return a.w < b.w end)

function raffle(table)
	local total_rate = 0

for i = #table, 1, -1 do
        total_rate = total_rate + table[i].w
	end

math.randomseed(os.time())

local c = 0 -- cumulative probability
	local randf = math.random()

for i = #table, 1, -1 do
        c = c + table[i].w / total_rate

if (randf <= c) then
            return table[i]
		end
	end
end

print(raffle(items).id)


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