curry.lua

local function curryWithNumberOfArgs(callback, numArgs)
	local function curried(...)
		local passedArgs = table.pack(...)

		if passedArgs.n > numArgs then
			error("too many arguments passed to curried function (called after already ran)")
		elseif passedArgs.n == numArgs then
			return callback(...)
		end

		return function(...)
			local allArgs = { unpack(passedArgs) }
			local newArgs = table.pack(...)

			for index = 1, newArgs.n do
				table.insert(allArgs, newArgs[index])
			end

			return curried(unpack(allArgs))
		end
	end

	return curried
end

local function curryUnknownArgs(callback)
	return function(...)
		local passedArgs = table.pack(...)

		return function(...)
			local allArgs = { unpack(passedArgs) }
			local newArgs = table.pack(...)

			for index = 1, newArgs.n do
				table.insert(allArgs, newArgs[index])
			end

			return callback(unpack(allArgs))
		end
	end
end

local function curry(callback, numArgs)
	if numArgs == nil then
		return curryUnknownArgs(callback)
	else
		return curryWithNumberOfArgs(callback, numArgs)
	end
end

return curry

curry.spec.lua

local ReplicatedStorage = game:GetService("ReplicatedStorage")

local curry = require(ReplicatedStorage.Libraries.curry)

return function()
	local function add(a, b, c)
		return a + b + c
	end

	it("should properly curry when passed each argument individually", function()
		expect(curry(add, 3)(1)(2)(3)).to.equal(6)
	end)

	it("should properly curry when passed argument in packs", function()
		expect(curry(add, 3)(1)(2, 3)).to.equal(6)
	end)

	it("should assume the second call time is the last one if no number of arguments are given", function()
		expect(curry(add)(1)(2, 3)).to.equal(6)
	end)
end