Stream composition in Elixir

There are 2 means of composing streams, you can zip them or concatenate them.

Only of those makes sense in your case.

You can filter the resulting stream into another Stream.

Please take a look at

• Stream.concat/2: Stream — Elixir v1.20.2
• Stream.zip/2: Stream — Elixir v1.20.2
• Stream.filter/2: Stream — Elixir v1.20.2

iex(63)> s1 = Stream.repeatedly(fn -> :rand.uniform(100) end)
#Function<54.33009823/2 in Stream.repeatedly/1>
iex(64)> s2 = Stream.repeatedly(fn -> :rand.uniform(100) end)
#Function<54.33009823/2 in Stream.repeatedly/1>
iex(65)> s3 = s1 |> Stream.zip(s2)
#Function<69.33009823/2 in Stream.zip/1>
iex(66)> s4 = Stream.map(s3, fn {a, b} -> a + b end)
#Stream<[
  enum: #Function<69.33009823/2 in Stream.zip/1>,
  funs: [#Function<49.33009823/1 in Stream.map/2>]
]>
iex(67)> s5 = Stream.filter(s4, fn x -> rem(x, 2) == 0 end)
#Stream<[
  enum: #Function<69.33009823/2 in Stream.zip/1>,
  funs: [#Function<49.33009823/1 in Stream.map/2>,
   #Function<41.33009823/1 in Stream.filter/2>]
]>
iex(68)> Enum.take(s2, 5)
[31, 48, 21, 15, 7]
iex(69)> Enum.take(s3, 5)
[{97, 90}, {22, 37}, {11, 100}, {12, 44}, {24, 83}]
iex(71)> Enum.take(s4, 5)
[109, 62, 79, 105, 178]
iex(72)> Enum.take(s5, 5)
[144, 68, 34, 104, 50]

Aha! Both excellent answers. Thank you