names.rb

list = ([ {name: 'Bart'}, {name: 'Lisa'}, {name: 'Maggie'} ])
list2 = ([ {name: 'Bart'}, {name: 'Lisa'} ])
list3 = ([ {name: 'Bart'} ])
def transform set
  names = ''
  list_length = set.length
  set.each_with_index do |name, index|
    if index + 2 == list_length
      name[:name].insert(-1, " & ")
    elsif index + 1 != list_length
      name[:name].insert(-1, ", ")
    end
    names << name[:name]
  end
  puts names
end

transform list
transform list2
transform list3