Chain all iterator in array that isn't determinate in compilation-time

[xqyww123]

I have an array of iterators depends on user's input, so cannot be determinate in compilation-time, and now I want to chain all of them together.

arrs = [] of Array(Int32)
gets.not_nil!.to_i.times {|a| arrs << [a] }

def chain_all1(arrs)
    arrs.each.map(&.each).reduce{|a,b| a.chain b}
end
def chain_all2(arrs)
    iter = arrs.each
    ret = iter.next
    return if ret.is_a? Iterator::Stop
    ret = ret.each
    until (a = iter.next).is_a? Iterator::Stop
        ret = ret.chain a.each
    end
    ret
end
chain_all1(arrs).each {|a| p a }
chain_all2(arrs).each {|a| p a }

The first one chain_all1 triggers a compilation error :

type must be Indexable::ItemIterator(Array(Int32), Int32), not (Indexable::ItemIterator(Array(Int32), Int32) | Iterator::Chain(Indexable::ItemIterator(Array(Int32), Int32), Indexable::ItemIterator(Array(Int32), Int32), Int32, Int32))

And for the second one chain_all2, compiler traps into a long time silence and ends in generic type too nested.

It's yet another recursive type problem, because Iterator tries to expand all code and it's impossible.

But 'chains all' is in fact practicable, by a struct stores all the iterators and implements next and rewind via a loop.

The code to implement a struct could be long, so I think it's should be implemented in std-lib, and a method chain(iterators : Enumerable(Iterator)) may be provided.

[xqyww123]

I just implemented a version with simple spec. here