`n + … + 0` in JS

benchmark.coffee

sum = require './sum'

for name, fn of sum
	start = Date.now()
	i = 500000
	while i > 0
		n = fn 1000, 0
		i--
	end = Date.now()
	console.log name, end - start

results

recursive 2817
tailCall 4337
normal 905
trampoline 5359
trampoline2 4104

sum.coffee

recursive = (n) -> if n is 0 then 0 else n + recursive n - 1

tailCall = (n, acc) ->
	if n is 0 then 0
	else
		acc += n--
		tailCall n, acc

normal = (n) ->
	v = 0
	while n > 0
		v += n--
	return v

trampoline = (n) ->
	acc = 0
	iteratee = ->
		acc += n
		n--
		iteratee
	iteratee = iteratee() while n > 0
	return acc

trampoline2 = (n) ->
	acc = 0
	iteratee = ->
		acc += n--
		undefined
	iteratee() while n > 0
	return acc



module.exports = {recursive, tailCall, normal, trampoline, trampoline2}