Module:MathUtil

---
-- @Liquipedia
-- wiki=commons
-- page=Module:MathUtil
--
-- Please see https://github.com/Liquipedia/Lua-Modules to contribute
--

local MathUtil = {}

--[[
Returns the base 2 log of the input number, rounded down.

Example:
MathUtil.ilog2(8) -- Returns 3
MathUtil.ilog2(24) -- Returns 4
]]
---@param x number
---@return integer
function MathUtil.ilog2(x)
	return math.floor(math.log(x) / math.log(2))
end

--[[
Returns the sum of an array.

Example:
MathUtil.sum({3, 5, 4})
-- Returns 12
]]
---@param xs number[]
---@return number
function MathUtil.sum(xs)
	local sum = 0
	for _, x in ipairs(xs) do
		sum = sum + x
	end
	return sum
end

--[[
Computes the partial sums of an array. The result is an array one longer than
the input.

Example:
MathUtil.partialSums({3, 5, 4})
-- Returns {0, 3, 8, 12}
]]
---@param set number[]
---@return number[]
function MathUtil.partialSums(set)
	local sum = 0
	local sums = {0}
	for _, num in ipairs(set) do
		sum = sum + num
		table.insert(sums, sum)
	end
	return sums
end

--[[
Returns the (standard) dot product of two vectors.

Example:
MathUtil.dotProduct({3, 2, 4}, {5, 6, 7})
-- Returns 55
]]
---@param xs number[]
---@param ys number[]
---@return number
function MathUtil.dotProduct(xs, ys)
	local sum = 0
	for i = 1, math.min(#xs, #ys) do
		sum = sum + xs[i] * ys[i]
	end
	return sum
end

---Rounds a number to specified precision
---@param value number
---@param precision number?
---@return number
function MathUtil.round(value, precision)
	local rescale = math.pow(10, precision or 0);
	return math.floor(value * rescale + 0.5) / rescale;
end

return MathUtil