ProjectEuler in Elixir

Problem 1 - Multiples of 3 and 5.exs

1..1000 - 1 |> Enum.filter(fn x -> (rem x, 3) == 0 || (rem x, 5) == 0 end) |> Enum.sum

Problem 2 - Even Fibonacci numbers.exs

Stream.unfold({1,2}, fn {a,b} -> {a, {b, a + b}} end) 
|> Stream.take_while(&(&1 < 4000000)) 
|> Stream.filter(fn e -> rem(e, 2) == 0 end) 
|> Enum.sum

Problem 25 - 1000-digit Fibonacci number.exs

Stream.unfold({1, 1, 1}, fn{i, a, b} -> {{i, a}, {i + 1, b, a + b}} end) 
|> Enum.find(fn{_, e} -> (to_string(e)|> String.length()) == 1000 end) 
|> elem(0)

Problem 4 - Largest palindrome product.exs

(for i <- 999..1, j <- i..1, do: i * j) 
|> Enum.uniq 
|> (Enum.sort &(&1 > &2)) 
|> Enum.find(fn e -> e = to_string(e); e == String.reverse(e) end)

Problem 6 - Sum square difference.exs

range = 1..100; (s = range |> Enum.sum; s * s) - (range |> Enum.map(&(&1*&1)) |> Enum.sum)