ruby-stream

Lazy stream implementation for Ruby because Enumerators are kinda silly.

Description

Streams are infinite, lazily evaluated, awesome lists. Here's an example of a Stream that represents the set of positive integers:

def int_stream(i)
  Stream.new(i) do
    int_stream(i + 1)
  end
end

integers = int_stream(1)

You can access streams like any other data structure:

integers[0] # => 1
integers[12] # => 13
integers[999999] # => 999998

Each value will be lazily calculated by materializing the Streams values until the requested value. Streams are stateless so a Stream will recalculate for every access.

You can also create finite Streams from infinite ones:

integers.take(5)

Finite streams have some extra functionality due to their ability to end:

integers.take(5).each do |i|
   puts i
end

integers.length # => 5

Infinite Streams also support interation and length calculations but you will need to be prepared to wait, forever. No seriously, I mean for all time. Its infinite.

Streams become most powerful when used with high order functions. At the moment ruby-stream supports map and filter operations that operate as they would on normal collections (these operations will only actually be applied to Stream elements on access or iteration however).