I’m trying to generate a list of numbers, where each number is a percentage smaller than the previous. Starting with 1. In the end I’ll need 10 (or whatever amount) of items from the end of it. The math formula I came up with for a single number looks pretty simple: Xn+1 = Xn - Xn * S S = 0.008 X0…

:waving_hand: Not sure if that’s what you are looking for, but I think the formula for x_n is x_n = x_0 * (1 - S)^n: x_1 = (1 - S) * x_0 x_2 = (1 - S) * x_1 = (1 - S) * (1 - S) * x_0 x_3 = (1 - S) * x_2 = (1 - S) * (1 - S) * x_1 = (1 - S) * (1 - S) * (1 - S) * x_0 ...etc And ignoring math, gene…

Hey @KristerV . You can use Stream.iterate/2 here. iex> x0 = 1.0 iex> s = 0.008 iex> stream = Stream.iterate(x0, &Float.round(&1 * (1 - s), 3)) iex> Enum.take(stream, 3) [1.0, 0.992, 0.984]

This would certainly benefit from a better explanation of your goal(s) with this. Though the code you did post can (for the most part) be written with higher level primitives. min_mid_price = Decimal.div("0.001", "2") |> Decimal.mult("0.123") |> then(&Decimal.sub("0.123", &1)) levels_total = 2 * 2…

awesome @ruslandoga that’s it! does it have a name? very useful. @freevova and @LostKobrakai the Stream.iterate i wasn’t aware of, will provide useful for sure.

[image] KristerV: does it have a name? https://www.thoughtco.com/calculate-decay-factor-2312218

Hello ! I tried the solution defmodule Series do def generate(x, s, count) when count > 0, do: [x | generate(x * s, s, count - 1)] def generate(_, _, _), do: [] end and was expecting to blow the stack since it isn’t tail optimized when run with a big count (like 100000); however it worked fine…

There’s some discussion about this in the Erlang Efficiency Guide ; short short version tail recursion isn’t necessarily faster or more memory-efficient.

Yes but since this is not a tail-recursive function should it blow the stack ? Is the erlang stack unlimited ? I tried it with really big numbers and I have a memory consumption of like 4 GB for that program but it seems to be working without breaking (!)

[image] spapas: Yes but since this is not a tail-recursive function should it blow the stack ? The BEAM doesn’t pass everything via the stack, it has registers as well. The BEAM book has a good introduction to the situation. You can go down this rabbithole further with compiler options - add…