Question

For example, if I have an array like this:

[:open, 1, :open, 2, 3, :close, 4, :close, :open, 5, :close]

I want to get this:

[[1, [2, 3], 4], [5]]

The :open effectively becomes [ and :close becomes ]

Answer 1

You could probably do this with a stack, but it’s pretty easy to design recursively:

#!/usr/bin/env ruby

x = [:open, 1, :open, 2, 3, :close, 4, :close, :open, 5, :close]

def parse(list)
  result = []
  while list.any?
    case (item = list.shift)
    when :open
      result.push(parse(list))
    when :close
      return result
    else
      result.push(item)
    end
  end

  return result
end

puts parse(x).inspect

Note that this will destroy your original array. You should clone it before passing it in if you want to preserve it.