ruby-flatten-array.rb

def flatten(a)
  out = []
  if !a.kind_of?(Array)
    puts "not an array"
    return -1
  end 
  a.each do |val|
    out +=  _flatten(val)
  end 
  out 
end

def _flatten(val)
  out = []
  if val.kind_of?(Array)
    val.each do |_val|
      out += _flatten(_val)
    end 
  else
    out << val 
  end 
  out 
end

#a = [1,2,[[3],4]]
a = "pocha"
puts flatten(a).inspect