Feature #11797
closed`Enumerator#with_object` with multiple objects
Description
Sometimes, when working with Enumerator#with_object
, I want to keep some additional temporary objects besides the one to return. A use case is as follows (I got this from this StackOverflow question: http://stackoverflow.com/questions/3418123). Suppose I have an enumerator created from an array:
e = ["a", "b", "c", "c", "a", "c"].to_enum
and want to get an array of its repeated elements in the order they are repeated (i.e., appears for the second time):
# => ["c", "a"]
I can do it using Enumerator#with_object
like this:
e.to_enum.with_object([{}, []]){|c, (h, a)| h[c] ? a.push(c) : h.store(c, true)}.last.uniq
Here, I am getting the array referred to as a
in the block, but besides that, I am using a temporal hash h
. I thought it would be nice if Enumerator#with_object
accepts one or more objects, pass them individually as block arguments, and returns only the last argument so that I can do this:
e.to_enum.with_object({}, []){|c, h, a| h[c] ? a.push(c) : h.store(c, true)}.uniq