local count = require "Module:fun".count

local function errorf(level, ...)

if type(level) == "number" then

return error(string.format(...), level + 1)

else -- level is actually the format string.

return error(string.format(level, ...), 2)

end

end

local varargs_or_array_mt = {

__index = {

arr_func = function (self, arr, i, j)

i = i or 1

j = j or #arr

assert(i > 0 and j > 0)

if i == j then

return arr[i]

elseif i < j then -- |---i+++j---|

return self.varargs_func(unpack(arr, i, j))

else -- |+++j---i+++|

return self.varargs_func(self.varargs_func(unpack(arr, 1, j)),

self.varargs_func(unpack(arr, i)))

end

end,

},

__call = function (self, ...)

if type(...) == 'table' then -- if first argument is table

if select(2, ...) then -- if second argument

return self:arr_func(...)

else

return self.varargs_func(unpack((...)))

end

else

return self.varargs_func(...)

end

end,

}

local function make_arr_and_varargs_func(varargs_func)

return setmetatable({ varargs_func = varargs_func }, varargs_or_array_mt)

end

local function sum_varargs (...)

local result = 0

for i = 1, select('#', ...) do

result = result + select(i, ...)

end

return result

end

local ops = {

sum = make_arr_and_varargs_func(sum_varargs),

mean = make_arr_and_varargs_func(

function (...)

return sum_varargs(...) / select('#', ...)

end),

min = make_arr_and_varargs_func(

function (...)

local min = math.huge

local min_index

for i = 1, select('#', ...) do

local val = select(i, ...)

if type(val) == "table" then

val, i = val.value, val.index

end

if val < min then

min = val

min_index = i

end

end

return { value = min, index = min_index }

end),

max = make_arr_and_varargs_func(

function (...)

local max = -math.huge

local max_index

for i = 1, select('#', ...) do

local val = select(i, ...)

if type(val) == "table" then

val, i = val.value, val.index

end

if val > max then

max = val

max_index = i

end

end

return { value = max, index = max_index }

end),

}

local stats_mt = {}

stats_mt.ops = ops

function stats_mt:__index(key)

if type(key) ~= "string" then

return nil

end

-- Parse field names such as "above_10" or "below_60".

local op, amount = key:match("(%a+)_(%d+)")

if amount then

amount = tonumber(amount)

local count =

op == "above" and count(function(val) return val > amount end, self)

or op == "below" and count(function(val) return val < amount end, self)

or errorf("Unrecognized operation %s", op)

self[key] = count

return count

end

-- Parse field names such as "mean" or "summer_min".

local season

season, op = key:match("^(%a-)_?(%a+)$")

if not (season == "" or season == "summer" or season == "winter") then

errorf("Unrecognized season %s", season)

elseif not ops[op] then

errorf("Unrecognized operation %s", op)

end

local result

if season == "" then

result = ops[op](self)

else

result = ops[op](self, unpack(self[season .. "_months"]))

end

self[key] = result

return result

end

local seasons = { summer = { south = { 10, 3 }, north = { 4, 9 } } }

seasons.winter = {}

seasons.winter.south = { seasons.summer.south[2] + 1, seasons.summer.south[1] - 1 }

seasons.winter.north = { seasons.summer.north[2] + 1, seasons.summer.north[1] - 1 }

setmetatable(stats_mt, {

__call = function (self, val, Southern_Hemisphere) -- constructor function

val = val or {}

local hemisphere = Southern_Hemisphere and "south" or "north"

val.summer_months, val.winter_months =

seasons.summer[hemisphere], seasons.winter[hemisphere]

return setmetatable(val, self)

end

})

return stats_mt

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