Haskell-style monad do-notation for Ruby

Example:

class Array
  include Monad

  def self.unit x
    [x]
  end

  def bind &f
    map(&f).inject([]){ |a,b| a+b }
  end
end

Array.run do
  x <- ["first", "second"]
  y <- ["once", "twice"]

  unit("#{x} cousin #{y} removed")
end

The above code returns the array:

["first cousin once removed",
 "first cousin twice removed",
 "second cousin once removed",
 "second cousin twice removed"]

For more examples, see the test suite.

By Aanand Prasad ([email protected])